Chapter 15: Evolutionary Perspectives

Important Discoveries in Neurobiology

• Natural Selection
• Architecture of the cerebral cortex
• Functional organization of the brain
• Kaas revised
• DNA structure
• Ethology and Neuroethology
• Sociobiology
• Evolutionary Psychology

Assumptions and Aims of Comparative Neuroscience

• Assumptions
• all behavior in all animals is generated by the nervous system
• brains evolve therefore behavior evolves
• we can gain insight just by studying animals
• Aims
• roots: history of brain and behavior
• rules: how did it change?
• relevance: generalizability

The Comparative Approach

Homology: the retention of a structure, behavior or gene from a common ancestor.

Convergent evolution: similar structures with similar functions can arise independently in different lineages

Out group comparison: phylogenetic relationships among animals

Adaptation and the Brain

Our behaviors are adapted to a simpler life. People are better at detecting some thing immoral rather than a simple logical task. Spatial abilities cary according to sex.

Evolutionary Insights into Human Brain Organizations

Many believe that bigger brains are better, but this appears to not be true. Human brains are larger because they need more problem solving capacity.

Chapter 14: Social Cognition

Self Perception and Self Knowledge


Self-referent effect: enhanced memory for information in relation to the self. There are two hypotheses explaining that memory for self is much better.

• the self represents the depth  of processing effect, memory is better as information is processed more deeply.
• processing information about the self is distinct from all other cognitive structures.

we are able to maintain a sense of self even if we have amnesia. R.B. and K.C.s personality judgments are consistent with judgments provided by their family members. But how accurate are our perception of self? We tend to claim more positive traits than negative to describe ourselves. The ventral anterior cingulate cortex was associated with baking positive judgments,

Perception of Other People

Even 4 month old babies show gamma activity in the occipital channels and late gamma activity over the right prefrontal cortex in response to direct eye contact. Premack  and Woodruff came up with the theory of mind, which describes our ability to make inferences about the mental state of others. Our understanding of others starts at a young age. The MPFC and the temporopatietal junction (rTPJ) in the right hemisphere are implicated.

Convergence in the Perception of Self and Others

Simulation theory: theory of mind is based on the ability to put ourselves in the shoes of another person. Empathy is an important trait to have in order to do this. Empathy is purposely putting yourself in another person's shoes in order to understand their thoughts and feelings. Mirror neurons seem to be important for our ability to empathize with others.

Social Knowledge

Utilization behavior is the extreme dependency on prototypical responses for guiding behavior. Patients with damage to the lateral prefrontal lesions used objects in a prototypical manner. Patients with damage to the orbitofrontal would talk about inappropriate topics. Damasio came up with the somatic maker hypothesis, which states that emotional information in the form of physiological arousal is needed o guide decision making. The Iowa Gambling Task is an example of this phenomenon. In this task, there are two piles for the participants to pick from. Normal patients learn to pick from the pile that maximizes winnings, but those with orbitofrontal damage could not learn to do this.

Neuroeconomics

People should make rational decisions: maximize their rewards and minimize their losses. The insula seems to be involved with negative emotions. 

Chapter 13: Cognitive Control

Working Memory


Miller looked at working memory in monkeys, he especially focused on the later PFC. He trained monkeys on a working memory task that required a successive coding of two stimulus attributes: identity and location. A sample stimulus is presented, then there is a 1 second delay then the objects are shown, one of which matches the sample. They must remember the position. He saw that there are three responses:

• "what" cells respond to specific objects, responses sustained over the delay period
• "where" selective to certain locations
• "what-where" cells respond to specific combo of what and where information

Recency Memory

Patients with frontal lobe lesions are impaired in the ability to organize and segregate events in memory. A recency task involving cards with 2 pictures are given to these patients. They are shown the cards and then are asked which object was most recently presented. People with frontal lobe damage did okay at the recognition task but are impaired at the recency task.

Source Memory

Source memory is about the context of the learning. Squire et al  looked at patients with frontal lobe damage. He gave them and normal patients facts to learn. After 6-8 days of retention interval, they were tested. When they answered the questions correctly they were asked where they had learned the information. Patients with frontal lobe damage performed as well as controls on recall but made mistakes on the source task. Glisky et al looked at just healthy patients but he grouped them into high and low functioning frontal lobes. They listened to sentences about common events, half were read by a women the other half were read by a man. They tested item memory by reading them a novel sentence paired with the study sentences. They were asked which one they had heard and who had read it. The two frontal lobe groups did not differ on recall but did differ on source memory.

Prefrontal Cortex

Patients are given a series of pictures containing letters and squares at random location. They must remember the order of the instruction-relevant stimuli.  If they had to remember the location of the squares activation is greater in the parietal and dorsal prefrontal regions. Remembering the letters caused greater activation in the temporal lobe and inferior frontal cortex of the left hemisphere.

• SPS: more activation for spatial
• IFG: ore activation for verbal
• APF: equal
• DLPF: pre activation when remembered backwards

In the n-back tests, patients needed to say which stimulus matched the stimulus n item ago. Activation in the lateral prefrontal cortex increases as the difficulty is increased.

Goal-Oriented Behavior

Wisconsin Card Sorting Task: cards vary along 3 dimensions: shape, color and numerosity. Participants had to sort the cards according to an experimenter-defined sorting rule. The experimenter says whether it is correct or incorrect after each card is played. After the participant has learned the rule, the experimenter will switch the rule again. Patients with frontal lobe lesions have difficulty with this task. They tend to perseverate, which is when they can not learn a new rule, they will apply the initial rule over and over.

Retrieval and Selection of Task Relevant Information

Art Shimamura: PFC can be conceptualized as a dynamic filtering. Focusing on what is important and filter out what is not relevant. Frontal lobes play a critical role in selecting task-relevant information. The stroop task is when colored words spell out color names. Name and colors to don match. Frontal lobe patients tend to have problems with this task.

Anterior Cingulate Gyrus

Operates as an executive attention system. Coordinates activity of others. Highest level of mental processes - it is the direct flow of traffic.

Chapter 12: Attention and Consciousness

Attention involves top-down (voluntary) goal-directed processes and bottom-up (reflexive), stimulus-driven mechanisms. They influence the way information is processed in the brain and can occur early during sensory processing. Balint's syndrome is a visual attention and awareness deficit. Someone who has this syndrome can only perceive one object at a time. 


Theoretical Models of Attention


Attention is defined as the ability to attend to somethings while ignoring others. There are three principle goals:

• To understand how attention enables and influences the detection, perception and encoding of stimulus events as well as the generation of actions based on the stimuli.
• To describe the computational processes and mechanisms that enable these effects.
• To uncover how these mechanisms are implemented in the brain's neuronal circuits and neural systems.

Herman von Helmholt

He did an experiment that looked at covert attention. He had participants look at a screen with letters different distances from the center. The screen was so large that the the participant could not view the screen in its entirety. Covert attention is defined as: the location to which the participant directed his/her attention could be different from the location at which he/she was looking. The participant could see the letters that were in his focus of attention better than those that were not.

E.C. Cherry

He looked at the cocktail effect, which is the idea that in a noisy environment people cal focus on a single conversation. The loudest inputs are not always the best and are not always the ones that everyone focuses on. The goal of the listener is to ignore the louder inputs, this is known as selective auditory attention. However, if the person you are talking to is boring you can attend to another conversation but still stare at the person who is talking to you. He observed the idea of dichotic listening: having two different inputs in each ear, but only attending one of those inputs. They are not able to repeat what was played in the unattended ear. However, you are able to pick up important information in an unattended ear, such as hearing your name.

Donald Broadbent

He came up with the model of selective attention, which states that there is a gating mechanism that determines what information is passed on for higher analysis. But, our mental capacity is limited so we filter our what we want and what we don't know, but some things that we don't want still get through.

Michael Posner

He came up with the spatial cuing paradigm. He carried out an experiment using cued stimuli. Participants are asked to stare at the cross in the center of the computer screen. A cue indicates where the subject should covertly attend. Then the target follows and it is either correctly or incorrectly cued. Posner found that the participants respond faster when it is correctly cued than when it is not.

Reflexive Attention

reflexive cuing: attention to an external stimuli. You will respond to the cue within 50-200 ms. He observed the phenomenon called inhibition of return, which states that you respond more slowly to target that have more space between them and the cues.

Anne Tresiman

She did an experiment that focused on the visual search paradigm. This is the idea that if something sticks out no attention is needed to find it. However, if there are more things that are alike it, it will take longer to find it; this is called conjunction search. 

Attention to Features and Objects.

If cued to expect the target is moving, will we be able to discriminate the target more readily than if it is unexpectedly not moving? Marissa Carrasco looked at this idea. There was a warning tone which was followed by one of three cues: target will not move, an arrow indicating which way it will move and a double-headed arrow indicating it will move left or right. She found that at the cue is not helpful at 150 ms, at 300 ms it helps for spatial but not feature. At 500 ms it helps for both.

Neurophysiology

Raul Hernandez-Peon predicted that: the olivocochlear bundle might exert top-down control over subcortical auditory regions that project to the cortex in the service of early attentional gating of auditory inputs. He found that the activity increases in the cochlear nucleus when the animals attended to the sounds rather than when they ignored the sounds while visually attending to the mice. So, attention to something else diminishes attention to other stimulus.

Steven Hillyard looked and auditory selective attention. He asked participants to attend to sounds in the left or right ear. The auditory sensory ERPs were increased in amplitude when stimuli were attended to compared with when they were ignored. He discovered the P20-50 effect: positive polarity latency between 20-50 ms suggests an early stage of processing. He localized the M20-50 effect to the auditory cortex in the Heschel's gyri.

It is hard to compare the auditory and visual systems because the timing is very different. In the voluntary visual attention, there are changes in the visual ERPs, which begin as early as 70-90 ms after the cue. This is known as the occipital P1, when a visual stimulus appears at a location to which a subject is attending, the P1 is larger in amplitude than when the same stimulus appears at the same location but attention is focused elsewhere.

How are feature and spatial attention related? Spatial attention produces the shortest latency ERP (N2pc). Wanted to see if features were selected before spatial attention was focused on target location. They saw that 140 ms after the onset, the feature ERP was generated in the ventral occipitotemporal cortex. 30 ms after that an N2pc response was generated in more anterior regions. This study indicated that the subjects were focusing spatial attention on the target. Feature selective attention precedes visuospatial attention when the location of the target is unknown in advance.

Neuroimaging

Spatial attention leads to activation in the extra striate cortex in the hemisphere opposite to the attended side (attention on the left enhances the right side, and vice versa). Spatial attention influences the processing of visual inputs. Kastner et al saw that in the absence of focused spatial attention, when stimuli are presented simultaneously, they can interfere with one another.

Corbetta et al saw that there are changes in the extra striate cortex when people attend to stimulus features. Selective attention to color, shape etc activate distinct regions of the extra striate cortex.

Attention to objects has been studied by John Duncan. Object properties are a collection of properties that make a person/object identifiable. Duncan compared attention to location to attention to objects. He found that two perceptual judgements about the same object can be made accurately, however they cannot be made accurately about two different objects. Uncued locations that were located on the same object showed an increased activity in the V1, V2, V3 and V4, but there was no activity in these areas when the uncued location was on different ojects.

Animal Studies

Moran and Desimone: they trained animals to attended to one stimulus and ignore another. They recorded responses in the V4. There is a stronger response in the V4 when the stimulus was attended as opposed to not. 

Brad Motter: activity in the V1 changes when competing stimuli were presented. Animals were trained to attend or ignore a stimuli. Motter recorded spike activity - when the animal was covertly attending, spikes were greater than when they were ignored. He also found that the amplitude of attention was alrger when competing stimlui were presented in the visual field compared to the target being alone.

McAdams and Reid: They also looked at the V1. They wanted to characterize the properties of the neurons in the V1 and then seeing if it was influenced by spatial attention. They trained monkeys to fixate on a central point and covertly attend to a black and white screen. A noise was presented to detect a small colored pixel. When the monkey saw the color pixel they were suppose to make a rapid eye movement from fixation to the location on the screen of the color. Spatial attention enhanced the responses of the simple cells but did not affect the spatial or temporal organization of their receptive fields.

Neurology and Neuropsychology of Attention

Unilateral spatial neglect is when one whole side of a person's visual world is gone. Typically the damage to the right parietal and frontal cortical areas are implicated, therefore the left visual field is gone. Some experiments have studied those with spatial neglect. They are given a line test and asked to intersect  the horizontal lines on the paper right in the center of the line. They tend to bisect the line more to the right side. You not only have neglect to external stimuli, but it is in your won memory as well. 

Chapter 10: Language

Thoughts are different than words. You may not be able to think of what you want to say but you still have the thoughts.


Aphasia


Aphasia is deficits in language comprehension and production. Broca's and Wernicke's Aphasia have been study quite a bit; Broca's Aphasia more than Wernkicke's.


Broca's Aphasia is an impairment in syntax. Syntax is important to convey they meaning of something and when you lose the meaning you lose syntax. They have difficulty in finding the words that they want. Broca believed that this was caused by cortical damage in the inferior frontal lobe, but there is more that is involved than Broca thought. By the Twenty Century researchers found that there were deficits in the insular cortex, lenticular nucleus of the basal ganglia and the fibers of passage.


Wernicke's Area includes the poterior third of the superior temporal gyrus. Evidence has shown that you can have Wernicke's Aphasia even without damage to the areas that are believed to be a part of the Wernicke's Area.


Semantic versus Syntactic Processing


Semantic = N400, which processes meaning and the Syntactic = P600 focuses on the appearance. They had subjects read sentences and their EEGs were averaged over time. WIth a word that does not fit in the sentence (anomalous word) there was a negative deflection in the N400 and with the word that was larger than the rest of the words there was a positive wave in the P600. the Semantic effect came before the syntactic effect. Research has shown that any words that are surprising in meaning get a wave.

Chapter 9: Emotion

Urbach-Wiethe Disease


Urbach-Wiethe disease is an impairment in perceiving others' emotions. SM had bilateral damage to the amygdala. His intelligence scores were normal but he was not able to understand fear. 


Basic Emotions and the Dimensions


There are six basic human facial expressions: anger, fear, disgust, happiness, sadness and surprise. There are two basic dimensions for emotions. Valence, which distinguishes between pleasant and unpleasant emotions and arousal, which is how intense the emotional response is.  Richard Davidson has two other items: withdraw and approach. Approach is the idea that stimulus that is either happy or surprising leads us to approach the situation, but fear and disgust leads us withdraw from the situation. Typically, withdraw goes hand-in-hand with negative valence.


Limbic System


James Papez come up with the circuit theory of brain and emotion. It says that emotional responses involve a network of brain regions. Including the hypothalamus, anterior thalamus, cingulate gyrus and the hippocampus. However, there is not much evidence that shows the hippocampus plays a role in emotion.


Amygdala


Heinrich Kluver and Paul Bucy damaged the amygdala in monkeys and observed the deficit called psychic blindness. They found that they tended to approach items that would usually elicit a fear response. However, the lesions may have been sloppy; they probably damaged the surrounding areas of the amygdala as well as the amygdala itself.


Others have done studied fear conditioning in rats. Before training a light was shown and the rats showed no response; however, with the foot shock and loud noise they did show a response. During the training the paired the light and shock, which elicited a fear response. Eventually the light alone would produce the same response. When the light and sound were paired it also produced a fear response, this is called the potentiated CR. They learned response was impaired when the amygdala is damaged. 


SP had bilateral damage to the amygdala. SP was unable to recognize fear in faces. During the learning phase they were just shown a picture of a blue square. During the acquisition phase, they were given a shock to the rest and the end of the presentation of the blue square. They had a normal response when the shock was presented but there was no change when the blue square was shown. SP has declarative knowledge but no behavioral response. Patients with bilateral damage to the hippocampus and not the amygdala produce a normal behavioral response but they cannot explain why they responded that way.


Social Response (facial expressions and social grouping)


When presented a picture of a face with a fearful expression, the amygdala will increase in response. The deficit is only with the recognition of facial expressions because they are able to generate and communicate their own facial expressions.  The reason SM may not be able to recognize fear is because fear is mostly shown in the eyes. Other emotions are shown in other parts of the face. SM did not focus on the eyes, instead they looked at other parts of the face.


Behavioral research examines behavioral responses that demonstrate preference for one group over another. Bias is calculated by the difference in the response latency between the black + good/white +bad trials versus the black + bad/white + good trials. Elizabeth Phelps used an MRI to see activation in white subjects when viewing black and white faces. When these subjects saw a picture of an unfamiliar black face the amygdala was activated. 

Chapter 8: Learning and Memory

Learning is the process of acquiring new information and the outcome is memory. There are three stages of learning: (1) Encoding: process the information. There are two steps to encoding acquisition, which registers the inputs and consolidation, which strengthens the representation of the information. (2) Storage: record the information. (3) Retrieval


Short-term Memory


STM is dissociable from LTM. STM turns into LTM eventually. GE had a tumor in the left angular gyrus, affecting the inferior parietal cortex and posterior superior temporal cortex. He had deficits in STm but no in LTM.


Working Memory


Baddeley and Hitch said that there are three components for working memory. The central executive controls the phonological loop, which deals with what we hear and the visuospatial sketch pad deals with what we see. Different lesions of the brain produce different deficits in the process. Lesions to the left supramarginal gyrus produces deficits in the phonological loop. Lesions to the parieto-occipital region (mostly in the right hemisphere than the left) produces deficits in the visuospatial sketch pad.


Long-term Memory


There are two parts of LTM - declarative and nondeclarative memory. Declarative memory is our conscious memory and it plays a big role in our social interchange. It looks as if the medial temporal lobe is important to declarative memory. Declarative memory can be broken down into two different parts; episodic (events in our lives) and semantic (world knowledge) memory. Nondeclarative can be broken down to two different parts: procedural memory and perceptual representation system. Procedural memory is learning motor and cognitive skills. Perceptual representation system is the idea that the structure and form of an object or words can be primed by prior experience.


Memory and the Brain


RB had lesions in the hippocampus, more specifically the CA1 pyramidal cells. It seems as if the hippocampus is important when forming LTM. Korsakoff's Syndrome is associated with alcoholism. It causes a thiamine deficiency which leads to the degeneration of the diencephalon, especially the dorso medial nucleus of the thalamus and mammilary bodies.


Consolidation


Consolidation is the solidification of memories to LTM. Evidence from patients who have done ECT shows that memories must be consolidated. THey found that retrograde amnesia is more likely to affect items that were learned close to the time of the ECT. Semantic information is consolidated in the temporal neocortex. 


Learning New Declarative Information


KC had a loss of episodic memory but his semantic memory was intact. Semantic memories are established because of episodic memories. KC had damage to the medial temporal lobe, left dorsolateral prefrontal cortex, premotor cortex and the parietal and occipital cortices. This produced severe anterograde and retrograde amnesia.


Beth, Jon and Kate (all siblings) had hippocampal damage. They could learn semantic information but they did not know where it came from, which is called source amnesia. 


Learning New Nondeclarative Information


HM can learn new things but he could not say how he know the task. He was asked to do a mirror task and he got better every time he had to carry out the task. So his procedural memory is intact but his declarative memory is lost.


Mortimer Mishkin (1978)


He removed the hippocampus, amygdala or both in monkeys. The monkeys were tested in the delayed nonmatch-to-sample task. The card is placed over the reward (food) then the door is opened. The monkey has to pick where the reward is in order to get the food. The door is closed again and a new object is introduced. The novel card is placed over the reward and after a delay the door is reopened. The monkey has to pick the novel card in order to get the reward. After training, the monkey is able to pick the new item to get the reward. If the hippocampus and the amygdala is damaged memory was impaired.

Chapter 7: The Control of Action

Movement


An effector is a part of the body that can be moved. An alpha motor neuron takes place between the muscles and the nervous system, which is the primary interaction between the two. It start at the spinal cord and exits through the ventral root and finally ends in the muscle fibers. In order for a muscle to move and excitatory signal is activated and the other is accompanied by inhibitory signals.


Sherrington


He damaged the spinal cords in cats and dogs, which disconnected the peripheral motor structures. He wanted to see if the animals were able to move without the higher level commands. The stretch reflexes remained intact. He saw that they could alternate the movements of their hind limbs. For example: one leg flexed and the other was extended, then the first leg extended while the other flexed.


Thomas Brown


He found that movements did not require sensory signals. He sectioned spinal cords and the dorsal root and animals could still make walking movements. He called these the central pattern generators. These are neurons in the spinal cord that can carry out a sequence of actions with no external feedback signals.


Emilio Bizzi


He experimented with deafferented monkeys. They were trained in a pointing experiment, but a torque motor counteracted their movements, but the monkeys were unaware this. When the torque motor was on the limb stayed in the same place and could not move. However, if it was off the limb would quickly move to the correct location.


Apostolos Georgopoulos


He tested monkeys on the center-out task. First, the monkey had to love the lever to the center. Then a light illuminated one of the eight target positions. Then the monkey had to move the lever to the illuminated position in order to get the reward. While the monkeys were carrying out this task Georgopoulos was recording cell activity. He found that activity in the cell in the motor cortex is strongly correlated to movement rather than location and it was even the activity was even stronger when the animal moved the lever towards itself. 


Brain Machine Interface (BMI)


Monkeys have learned to move computer cursors and even prosthetic limbs just by thinking. This revolutionary idea can be a great help to those with amputated limbs. However, it is hard to move from animals to humans. 


Rizzolatti


He studied monkeys and studied whether or not neurons activated while observing someone carry out an action. The neurons in monkeys responded similarly when the monkey cracked the peanut itself,  watched someone crack it, watch someone crack it but could not hear it and could hear the peanut being cracked but could not see it. He called these mirror neurons.


Planning and Execution of Movement


Individuals were taught a complex sequence of finger movements. When TMS is used to disrupt the motor cortex the individual knew what to do but something stopped them. When the supplementary motor area was disrupted they lost track and could not remember the goal. However, activation depends on how much it is based on memory. How well you know a certain action changes in the brain. A novel action start in the PMC but when you start to know something better it moves to the SMA.


Apraxia


Apraxia is a loss of motor skills. These individuals are not able to turn their thoughts into actions. One example is of a patient with bilateral lesions of the parietal lobes. She was a fish filleter and one days she started to cut the fish when she all of a sudden stopped. She remembered how she needed to finish the task but she just could not execute it. 
Ideomotor apraxia is when the individual has an idea of the action but they cannot execute it properly. Ideation apraxia is more severe. It is when the patient's knowledge of an action is disrupted.


Basal Ganglia


The basal ganglia consists of five nuclei: caudate nucleus, putamen, globus pallidus, subthalamic nucleus and the substantia nigra. In Parkinson's disease the pathway from the substantia nigra to the striatum is destroyed. The substantia nigra produces most of the body's dopamine. This produces more excitation from the thalamus to the cortex, when then causes uncontrollable movements. There are two kinds of dopamine receptors, when one has Parkinson's the dopamine cannot cross the blood brain barrier. The medication one can take is called L-dopa. It is one step back from dopamine so it is able to cross the blood brain barrier. 


Those with Parkinson's have a motor impairment as well as a cognitive impairment.  Steven Keele tested patients in a shifting test. They had to learn two 3 movement sequence. Then they were asked to produce a six element sequence from the two movement sequences that they learned initially. Parkinson's patients had a hard time when they had to transition between sequences. This shows that they have a motor control impairment. Then they were tested on their cognition. They had to discriminate between either shapes or colors and they reaction time was recorded. Again, they were slow when they had to shift.

Chapter 6: Object Recognition

Agnosia: is a failure of perception, or “to experience a failure of knowledge”. For some, they are not able to develop a rational percept; others are not able to access the knowledge to identify an object.

Cortical Pathways

 The occipitotemporal pathway is for object perception and recognition. The occipitoparietal pathway is for spatial perception or determining where an object is. Typically, the parietal and periphery determine “where” and the temporal and fovea help to determine “what”.

Object Recognition

Apperceptive Agnosia: failure to recognize an object. One study tested people with apperceptive agonsia to see how well they are able to recognize an incomplete picture. Typically, they are not able to tell what they picture is until it is complete. Reseachers found that there is more of a deficit when the right hemisphere is damaged than the left hemisphere. Warrington also gave the Unusual Views Object Test to those with apperceptive agnosia and found that they are not able to recognize and object that is shown to them in an unusual view.

Associative Agnosia: have the correct information but are not able to access it. One study found that those with associative agnosia could point out an object when they were named but could not point out the object when asked if they were different.

Prosopagnosia: the inability to recognize faces. Not only can a damaged brain cause prosopagnosia, but genes also play a role in this.  Two regions of the temporal lobe a activiated while looking at faces: the superior temporal sulcus and the inferotemporal gyrus.

Chapter 5: Sensation and Perception

Olfactory Perception

The sense of smell is more primitive than any other senses we have. First, the odor molecules enter the nasal cavity. The odorants attach to the olfactory epithelium, which are odor receptors. There are thousands of odor receptors; each respond to certain number of odorants. When an odorant binds to a bipolar neuron, also known as an olfactory receptor, a signal is sent to the neurons in the olfactory bulb, which are called glomeruli. They then leave the olfactory bulb and go to the primary olfactory cortex. The primary olfactory cortex is located at the intersection of the frontal and temporal cortices. Then the neurons in this area connect to the orbitofrontal cortex, which is considered the secondary olfactory processing center.

There are a few reasons why olfactory perception has not been studied as much as the other senses. It is hard to control how much of an odor you are giving to a participant. It is also hard to know when an odor is no longer present. Most odors are quite subtle and take investigating to identify and detect the smell.

Vision

Vision is the most studied out of all the senses. Visual information is in the light reflected from objects. As light passes through the eye, the image in inverted and projects on the retina. Photoreceptors can be found in the deepest layer of the retina. There are two types of photoreceptors: rods and cones. Rods are most effective with lower levels of light; however, cones are sensitive to higher levels of light. The fovea contains many cones. The optic nerve transmits visual information to the central nervous system. Since the retina is curved the temporal half of either the left or right retina is stimulated by the opposite visual field. Each optic nerve splits into different pathways depending where they terminate in the subcortex. Most of the axons are projected from the retina to the lateral geniculate nucleus. The remaining axons stimulate other subcortical structures.  The final projection to the visual cortex is through the geniculocortical pathway and then heads to the primary visual cortex.

The area that is activated in the color foci is called area V4 and the area activated in the motion task is area V5. There is a big difference between species when it comes to the position of the color and motion areas in the brain.

Achromatopsia is a deficit in seeing color. People with achromatopsia have lesions around the V4 area. One study found that individuals are better at differing reflectance differences than they are at distinguishing hue differences. Each subject was shown three color patches. Two of them were identical and the third was different in either hue or reflectance.

Akinetopsia is a deficit in motion perception. M.P. could not see objects moving at a continual speed; instead, she saw an object in one position and then another. She was not able to determine the direction or speed of a moving object. The area in the brain that was damaged was the area around the V5.

Chapter 4: Methods of Cognitive Neuroscience

Mental Representations in the Cognitive Approach


There are two key concepts that guide the cognitive approach. The first is: how we process information depends on what we know and the second: mental representations change over time. The Posner experiment showed that we can determine many representations of a stimuli (the physical aspect of the stimulus, the stimuli's identity and finally the category that the stimulus belongs too).


Another goal of cognitive psychology is to figure out how we perform tasks. Sternberg proposed four primary mental operations:


1. Encode: identify the object
2. Compare: the object with the objects stored in memory
3. Decide: if the object matches the items in memory
4. Respond: make a decision


How efficient is our brain at retrieving information? Two ideas were proposed: (1) if this is a parallel process then the reaction time should be independent of the number of objects in your memory (2) if it is a serial or sequential process reaction time should slow down as the memory set increases. Sternberg found that reaction time increased as the memory set increased.


Computer Modeling


Computer simulations are used to mimic the cognitive processes and that support a particular behavior. In order for this to be successful the creator must be very specific about how the information is represented and changes. Computer models show that minor changes in the brain could result in big behavior changes. People are even able to damage areas in the computer model to see how that affects behavior.


Animals in Experiments


Single-cell recording was a big breakthrough for Cognitive Psychology. In order to do single-cell recording, one must stick an electrode into a single. However, it may be hard to observe behavior because this technique may kill the cell. This technique has been used to study most regions of the brain. Many studies have looked into the visual systems. All cells that are visually sensitive can only respond to a stimuli in a certain region of space; this is called the receptive field.. The receptive field for cells vary; the smallest are in the primary visual cortex and the largest are in the association visual cortex.


Genetics play a role in cognitive function. Right now, neuroscientists  are working with animals  to identify  the genetic mechanisms in both the brain structure and function. Some are performing knockout procedures. This means that certain genes are manipulated so that they are know longer able to function.


Neurology


Most neurological studies see how much damage has been done and how it was done. Then they measure electrical activity and changes in behavior. Diffusion tensor imaging is done with  an MRI scanner. It looks at how big and active pathways are.


How does cognitive psychology play into neurology? If a patient has damage cognitive psychology can define the nature of the impairment. Obviously, if damage is done in a certain brain area and a behavior depends on that area the damage should disrupt the behavior. Single a double dissociations are helpful in studying damaged brain areas and cognitive tasks. In a single dissociation, two groups are tested on two tasks and there should be a difference between the groups. In a double dissociation, three groups are compared. One is a control group, group one is impaired at task A and group two is impaired at task B.


Localizing a certain area for a specific deficit is harder to do in groups. This is because no one has damage in the exact same area, psychologists have to isolate the a common area in order to pinpoint a certain damaged area for a certain deficit. However, with individuals you are able to focus on the one brain area that is damaged and understand that specific damaged area. Many wonder if the damage is specific to the individual or are you able to generalize it across people.

Chapter 3: Neuroanatomy and Development

Plasticity


Plasticity means adaptive or malleable. If an area on the body is destroyed the respective brain area will start working with the area next to it. Also, experience can shape the brain areas even in adult life. Topographic mapping is when the body is represented on its respective cortical area. This is also called homunculi, which is a when a "small person" is represented on the brain areas. For example, if one of your fingers is amputated or a nerve is cut the respective brain area will eventually become active again and respond to stimulation to the finger adjacent to the amputated finger.  The cortical neurons that responded to the amputated areas may undergo denervation hypersensitivity, which means that the receptors become more sensitive or there is an increase in number of receptors. Another example of brain plasticity is in string players. String players tend to use their left hands a lot and because of this that particular brain area  grows. Within days a certain brain area can adapt itself and become active and respond to stimulation to adjacent areas. Reorganization depends on the amount of gamma-aminobutyric acid (GABA). More GABA means that the ability of the brain to reorganize itself. 

Chapter 2: Cellular Mechanisms and Cognition

Neurons

The major parts of the neuron are the soma, dendrites and axons. Dendrites receive information from other neurons and axons pass the information on. The soma is the cell body. There are different forms of neurons. They are: unipolar, bipolar, pseudounipolar and multipolar. Unipolar neurons have only one process that extends from the cell body. Bipolar neurons have two processes that extends from the cell body. Pseudounipolar neurons look like unipolar neurons but were bipolar neurons. Their dendrites and axons have merged together. Multipolar have only one axon and have many dendrites extending from the cell body.

Resting Membrane Potential

There are ion channels that allow sodium, potassium and chloride either in or out of the cell. There is a higher concentration of sodium and chloride outside than there is inside. This is opposite for potassium, there is a lower concentration outside than inside. Because of the concentration differences potassium will enter the cell while sodium and chloride are pushed out. However, the cell would be a completely different cell if there were nothing to maintain the concentration difference. The pomp helps do this. Typically, the voltage for resting potential is about -70 millivolts. Since the cell has a concentration difference in ions the voltage changes, this is called the action potential. During action potential sodium enters into the cell increasing the voltage. It seems as if it is reaching the sodium equilibrium. However, when the voltage gets too high the pump kicks in and works to lower the voltage to its normal state.

Synaptic Transmission

The important function a neuron serves is communicating with other neurons. The action potential leads to the depolarization of the neuron, which initiates an increase in calcium. This causes small vesicles to fuse with the membranes at the synapse; in turn the transmitter is released into the synaptic cleft.  The chemical interaction can lead to either hyperpolarization or depolarization. Hyperpolarization (inhibition) is very important. If the neuron would fire continually, this would produce a seizure. If the postsynaptic cell is a neuron this will lead to excitatory postsynaptic potential (EPSP). However, if the neurotransmitter has an inhibitory action this will lead to a inhibitory postsynaptic potential (IPSP). Hyperpolarization will cause the membrane potential to become negative therefore farther away from threshold. This would decrease the chances of the neuron to produce an action potential. Sometimes inhibitory synaptic inputs lead to depolarization. This is because the equilibrium potential for chloride is about -60 millivolts. The resting potential is about -70 millivolts, so opening the chloride channels would cause the membrane potential to move towards -60 milllivolts. The chloride would force the potential to remain around -60 millivolts. The threshold to create an action potential is about -40 millivolts. So, depolarization to -60 millivolts would still lead to inhibition of the neuron.

Chapter 1: A Brief History of Cognitive Neuroscience

History of Cognitive Neuroscience


In the 70's Michael Gazzaniga and George Miller were riding in the back of a taxi in New York City on their way to a dinner for those who were studying how the brain enables the mind. That is when they came up with the term cognitive neuroscience. Cognition, meaning the process of knowing or how we came to knowing something and neuroscience, which is the study of the nervous system. Essentially, cognitive neuroscience means how the brain enables the mind.


The Brain Story


Localization and topographic maps are very important ideas when studying the brain. Localization is the idea that certain areas of the brain are responsible for specific things. Topographic organization is the belief that the brain is ordered in an orderly fashion that moves from one part to another. Topographic mapping also supports the idea of localization. A study that supports the idea of localization was when Paul Broca was treating a patient with damage to the left inferior frontal lobe. The patient could understand language but he was not able to speak. Carl Wernicke treated a patient with damage to the area where the parietal and temporal lobes meet. The patient had the opposite symptoms as Broca's patient. This patient could speak but they made little sense when speaking. These findings were a huge step in the study of the brain.