Chapter 2 - Cognitive Neuroscience Flashcards
what is cognitive neuroscience
the study of the physiological basis of cognition
what is the ‘levels of analysis’ approach?
why is it relevant for cognitive science?
- topics can be studied from different levels, ranging from micro (physical and biological processes) to macro structures.
- to fully understand anything, it must be studied at all possible levels of analysis
what are the two primary functions of the neuron
create and transmit information
what is a nerve net, and how was it discovered?
a network of neurons that appeared continuous due to the early method of dying neurons and looking through a microscope - couldn’t observe synapses
what was Golgi’s contribution to brain science methodology?
- why was this so useful?
developed a staining technique, immersing a thin slice of brain tissue in silver nitrate.
- less than 1% of the neurons would be stained
- stood out from the rest of the tissue
- stained completely as well, so they could make out their structure
what two techniques did Cajal use to investigate the nerve net?
- why was this so effective?
- Golgi’s staining procedure
- studied tissues from newborn animals (sparser cell distribution
- small % of staining + sparse neurons = very clear detail
what did Cajal discover about neurons?
individual units, not the nerve net
what do we call the doctrine that emerged from Cajal’s discovery that neurons were individual units?
the neuron dotrctine - individual cells transmit signals in the NS, these cells are not continuous
what were Cajal’s three conlclusions about neurons (other than their discreteness)
- discovered the synapse (gap btwn neurons)
- neurons are not connected indiscriminately, only connect to specific neurons that form higher order sets of connected neurons called neural circuits
- neurons that draw information from the environment also exits (receptors)
who was the first to record electrical signals in sensory neurons?
Edgar Adrian
explain Adrian’s method for recording neutrons electrical signals
micro electrodes (two of them)
- recording electrode - placed in a neurone to measure the impulse
- reference electrode - placed some distance away so as to be unaffected by the electrical signals
- difference in charge is the impulse
what is the difference in potential between the recording and reference electrodes when an axon is at rest?
- what do we call this?
(-70) mv (inside of the neuron is 70 mv more negative than the outside)
the resting potential
what does the microelectrode process register during a nerve impulse?
charge inside axon rises to 40 mv as the impulse passes the electrode, then returns to its resting potential
what do we call the full process of a nerve impulse?
ie, stimulation, electrical transmission down the axon
the action potential
how long to action potentials last?
1/1000th of a second
what is the importance of the action potential?
mechanism by which information is transmitted throughout the NS
what was another one of Adrian’s key findings about action potentials?
they maintain the same signal intensity across the length of the axon - ideal for sending signals over long axis, as it preserves informational content
what is the main interest of the cognitive neuroscientist in regards to neural impulses/
how they contribute to the operation of the mind
How did Adrian study how neural information is encoded?
by measuring the A.P’s of tactile neurons across the length while changing the pressure applied to the skin
- intensity of the individual action potentials remained the same, the rate of action potentials changed (more pressure meant more signals, vice versa)
What does Adrian mean when he says that neurons are representing their stimulus?
more stimulus intensity is associated with more frequent neural responses, so this is said to represent the intensity of the stimulus.
What questions can we ask to go beyond Adrian’s study of the magnitude of neural stimulus? (2)
- give a possible solution, and Adrians response
- how is the quality of experience represented by neural firing across the senses
- how is the quality of experience represented by neural firing within a given sense
- different shapes of action potential
- Adrian: no, all action potentials have essentially identical size and shape
What is the short answer to the question of how qualitative differences are represented by neural firing?
different qualities and aspects of experience activate different neurons and brain regions
what its he principle of neural representation
everything a person experiences is based on representations in that persons nervous system
what were the two facts researchers began to uncover when they started studying single neurons in the primary visual cortex?
- many neurons at higher levels of the visual system respond to complex stimuli (faces, gemetrical shapes)
- a specific stimulus causes distributed neural firing across the cortex.
what are feature detectors
neurons that respond to specific stimulus features, like orientation, movement or shape.
how did Hubel and Wiesel discover feature detectors?
presented visual stimuli to cats, and found that each neuron in the visual area of the cortex responded to a specific type of stimulation presented to a small area of the retina
what is experience dependent plasticity?
changes in Brian structure caused by experience
Explain Blakemore and Cooper’s study on experience dependent plasticity in cats?
reared cats in environments containing only vertical or horizontal shapes - became selectively aware of the shape orientation they were reared with, and had virtually no neurons that responded to the opposite stimuli
what do the results of Blakemore and coopers study on experience dependent plasticity suggest?
Perception is determined by neurons that fire to specific qualities of a stimulus
how many % of the cortex is comprised by the visual system/?
30%
Explain Gross’ findings on anaesthetized monkeys and complex images
presented stimuli to anaesthetized monkeys
- neurons in the temp lobe respond to complex stimuli (hand shaped stimuli with fingers pointing up)
- also found some that responded best to faces
explain hierarchical processing
- neurons in sensory cortexes respond to simple stimuli
- send this information to higher levels of the system where signals interact from several sources (respond to more complex signals)
- so on and so forth!
what is the sensory code
the process by which neurons represent various characteristics of the environment
what is specificity coding
neurons can respond selectively to specific stimuli
is specificity coding correct?
probably not; neurons usually respond to a number of similar things (like a set of faces) - would greatly increase the number of necessary neurons
what is population coding
the representation of an object by the firing patterns of a set of neurons
what are some advantages of population coding
- large number of stimuli can be represented as large groups of neurons can create a bunch of unique patterns of firing
- good evidence in other cognitive systems too
what is sparse coding
particular objects represented by a pattern of firing of only a small number of neurons, while most remain silent
- each neurone can respond to more than one feature
explain Quiroga et all 2008 findings on single neuron selectivity
found neurons that respond very selectively (like just to Micheal Scott)
- but only had 30 minutes to look, probably examples of sparse coding without enough time to test
is sparse coding limited to vision/
nope, also in aud and olfactory system
what is the difference between representing memories and representing experiences
perception is associated with a present stimulus, memory concerns a stimulus as represented already
- likely that population and sparse coding are operative here too, though
what is the localization of function
specific functions are served by specific brain areas
what is the main Brain area for cognitive function
cerebral cortex - 3mm thick layer of tissue covering the sub-cortical areas
explain the concept of cortical equipotentiality
an accepted idea in the 1800s that argued that the brain operated as an indivisible whole
How did Broca reject the concept of cortical equipotentiality
studied patients with brain damage due to stroke - caused damage to the frontal lobe structure called Broca’s area
- loss of ability to produce speech (slow, laboured and ungrammatical - Broca’s aphasia)
explain Wernicke’s aphasia
- dmg to which brain area, and the pathological outcome
damage to the area of the temporal lobe that result ied in fluent and grammatical speech that was incoherent
- also unable to understand the speech of others - can’t attach words to their meaning
damage to which brain structure resulted in blindness inn WW1?
occipital lobe, where the visual cortex is
did the specific area of the occipital lobe damaged influence the type of blindness?
yes, ex. damage to the left part resulted blindness in the upper right =part of visual space
where is the auditory cortex
upper temporal lobe
where is the somatosensory cortex
parietal lobe
what is the primary function of the f.lobe in perception
receiving information from the other structures, integration and higher cognitive functions
what is prosopagnosia and where does damage cause it
inability to recognize faces - due to damage to the tempora lobe on the lower right side of the Brian
explain double dissociation
occurs if damage to one area of the brain results in the loss of some function x while y remans, and vice versa for some other brain area
- need to find 2 people with brain damage to these 2 areas
- necessary to prove that a brain region serves a specific function
how do we use single neurons to determine localization
check the % of neurons that respond selectively to a given thing (say faces) in a specific region
Tsao (2006) - 97% of neurons inn the lower temporal lobe in monkeys respond to faces
explain fMRI
- neural activity increases brain oxygen in the active areas
added oxygen increases magnetic properties off hemoglobin - present a magnetic field to the brain these more magnetic oxygenated molecules respond more strongly and increases the fMRI signal - measure at voxels, which are small 3d sections of brain
what is task-relevant fMRI
the change inn brain activity that can be linked to the specific task at hand - measured by fMRI and some complex stats
what is the fusiform face area
the brain region responsible for facial recognition, in the fusiform gyrus on the bottom of the temporal lobe
- brain region damaged in prosopagnosia
pictures of visual scenes activate what area
parahippocampal place area
- codes information about spatial layout (activated when viewing empty and full rooms)
pictures of bodies or their parts (other than faces) active what area
the extra striate body area
explain Huth;s film experiment
showed people a movie while they were in fMRI - composed a list of more than 1000 objects and action categories and when they came up I the show
- found out which stimuli different voxels responded to
what is the paradox behind Huth’s experiment
- specific brain regions are responsible for the perception of specificc types of stimuli
- map stretches over a large area of the Cortex
what does the distribution of ‘human’ concepts in Huth;s experiment tell us?
experiences are multidimensional, and even simple experiences involve combining different qualities
what is distributed representation
the idea that a single experience activates several areas of the brain that may be widely separated
explain how distributed representation applies to memory
- STM and LTM are served by different brain regions
- thinking about episodic and semantic memories also activate different regions
- memories are multimodal - activate sensory, emotional, etc.
explain how distributed representation applies to producing and understanding language
- we have Broca and werneickes areas
- but language also involves communication between the two, connections iwht other areas
explain the specific findings related to the distributed representation of language (3)
- damage to areas other than B and W can cause problems with language (ross 2010)
- nonlinguistic functions are associated with B’s area
- sentence grammar is processed throughout the language system
explain the current neurological model of language
2 pathways
- involved in processing sounds, speech production, uttering words
- understanding words
- both involved in understanding sentences
what are neural networks
interconnected Brain areas that communicate with one another
- outcome of distributed processing; distributed regions must be able to communicate
what are the 4 principles of neural networks
- networks are complex structural pathways that form he brains ‘information highway’
- functional pathways within structural pathways that serve distinct functions
- networks operate dynamically, which mirrors the dynamic nature of cognition
- there is a resting state of brain activity
what is structural connectivity
- how do owe measure it?
the wiring diagram of the brain (synapses and such across brain areas)
- early researchers cut up brains to check these out
- now ; track-weight imaging - detects how water diffuses along the length of nerve fibres
-
explain connectome
the structural description of the network of elements and connections forming the human brain’
what is functional connectivity
measured by the degree to which two brain regions correlated - high correspondence means high functional connectivity
how does resting state firm measure functional connectivity
- use task related fmri to determine brain regions responsible for specific tasks - call this the seed location
- measure the resting state fmri of the seed
- measure the resting state fmri at another location (test location)
- calculate the correlation between seed and test location responses across a time axis
- can also be done with task related fmri between seed and test
does high functional connectivity imply structural connectivity
- but is there overlap between the concepts
no, could both be getting stimulated by some other region causing the overlap
- yes, they tend to correlate
what are the 6 common functional networks we’ve uncovered by resting state frmri
- visual
- somato-motor
- dorsal attentiuon (attention to visual stimuli and spatial location)
- Executive control - higher level cognitive tasks involved in working memory and directing attention during tasks
- salience - attending to survival relevant events
- default mode- mind wandering, coenobite activity related to personal life story, social functions, monitoring internal emotions states
what is meant by the dynamics of cognition? (2x)
flow of activity within the brain is dependent on the environment and mental states and is therefore dynamic, switching strucures on and off and such
- also slow changes; functional changes I memory networks are accumulated during the day and strngthened at night
what is the default mode network
network of structures that respond when a person is not involved in specific tasks
- composed of areas in the frontal and parietal lobes that decrease in activity during tasks
- DMN activity tends to result inn mind wandering
- mindwandering decreases task-relevant performance
