cognitive neuroscience

neural representations

the ways in which properties of the outside world manifest themselves in the neural signal.

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saccades

visually guided eye movements

modularity

the idea that different regions of the brain are specialised for different functions

cognitive neuroscience

aims to explain cognitive processes in terms of brain-based mechanics

cognitive neuropsychology

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study of brain damaged patients to inform theories of normal cognition

informational processing

approach in which behaviour is described in terms of a sequence of cognitive stages

domain specificity

idea that a cognitive process/brain region is dedicated to one type of information - FODOR

intereactivity

later stages of processing can begin before early stages are complete

top down processing

perceptions are heavily influenced by our expectations and prior knowledge, memory influences perception

neural network models

computational models where information processing occurs using many interconnected nodes

temporal resolution

accuracy with which one can measure when an event occurs

neuron

a nervous system cell with special properties that allow it to communicate with other cells

club synapse

place where axon meets dendrites

electrical signalling - action potentials

a sudden change in the electrical properties of the neuron membraine

spatial resolution

the accuracy with which one can measure where an event is occuring

chemical signalling process

1. action potengial reaches axon terminal, releasing neurotransmitters into the synaptic cleft
2. protein receptors in the dendritic membraine of the post synaptic neuron bind to the neurotransmitters, creating a synaptic potential

neurotransmitters - excitatory or inhibitory

1. excitatory :- make action potential more likely by making inside of post synaptic neuron more positiive
2. inhibitory:- make action potential more likely by making inside of action potential more negative

connectome

a comprehensive map of neural connections in the brain

graph theory

a math technique for computing the pattern of connectivity from a set of correlations

ventricles

hollow chambers of brain that contain cerebrospinal fluidspi

spiking rate

the informational code carried ny the neuron, the number of action potentials propergated per second

grey matter

contains neuronal cell bodies, outer layer

white matter

axon, myelin and glia (support cells involved with tissue repair)

cerebral cortex

the outside surface of the brain made up of four lobes and 2 hemispheres, each lobe characterised by a set of gyri (ridges) and sulci (valleys)

major subcortical structures

1. basal ganglia
2. limbic system
3. biencephalon

basal ganglia

subcortical region of grey matter involves with movement and complex motor control, additionall involved with value-based reinforcement learningli

limbic system

includes the amygdala and hippocampus. A subcortical structure that helps relate an organism to their present and past environment.

diencephalon

subcortical structure containing the thalamus and hypothalamus. Contains a variety of nuclei specialised for different functions, primairily for body regulation. Primary relay centre.

midbrain

connection central between brain and the spinal cord, subcortical route for hearing and gaze orientating

hindbrain

contains the pons, cerebellum and medulla oblongata. coordinates functions essential for survival

cerebellum

integrates information about motor commands with sensory feedback to enable smooth movement and dexterity, as well as balance and posture

superior colliculi

midbrain nucleus that forms part of the subcortical sensory pathway involved in programming fast eye movements

inferior colliculi

midbrain nuclius that forms part of subcortical auditory pathway

pons

link between cerebellum and cerebrum

voxel

volume based unit that brain is split into

vocel based morphometry

technique for segregating and measuring differences in white and grey matter connectivity

diffusion tensor imaging

uses MRI to measure white matter connectivity between neurons

fractional anisotropy

measure of the extent to which diffusion takes place in some directions more than others

examples of structural imaging

CT AND MRI

MRI

takes static images of the brain, slicing coronally. measures neural activity through tracking blood oxygen consumption. In order to compensate for increased oxygen consumption, more blood is pumped into the active region.

Directly measure concentration of deoxyhemoglobin in the blood

measures BOLD response

BOLD response

blood oxygen level dependent contrast

hemodynamic response

changes in BOLD response over time, has three phases


1. initial dip
2. overcompensation
3. undershoot

poor temporal resolution

good spatial resolution

fusiform face area

area in inferior temporal robes that responds more to faces than other visual objects and is implicated in processing facial identity, usually larger in the right hemisphere.

categorical perception

the tendency to pericieve ambiguous of hybrid stimuli as either one thing or the other, demonstrated by FFA

cognitive subtraction

acitivity in a controll task is minused from activity in an experimental task

pure insertion

the assumption that adding different componants to a task doesnt affect the operations of other componants

connective conjunction

to identify a set of tasks with a common proponant

efference copy

motor signal used to predict sensory concequences of an action

functional intergration

way in which different regions communicate with eachother

domain specificity

brain regions are specialised for the perception of particular stimuli

resting state paradigm

technique for measuring functional connectivity in which correlations between several regions are measured when participant is not performing a task

default mode network

a set of brain regions thats more hemodynamically active during rest than tasks

stereotactic normalisation

mapping individual brain differences only a standard template of brain anatomy

smoothing

redistributing brain activity from neigboring voxels to enhanse the signal-to-noise ratio

fMRI strengths

non-invasive

spatial resolution is goood, can begin to localise brain activity

lots of data

weaknesses

poor temporal resolution

some regions hard to image

noisy and claustraphobic

cannot use with metal implants

more activation doesnt mean more processing - region can be recieving input but not responding

shows whats involved but not whats crucial

family wise error (FWE)

correcting statistical comparisons based on number of tests

false discovery rate (FDR)

correcting statistical comparisons based on number of positive results obtained

inhibition

reduction of activity in one region due to activity in another region

activation/deactivation

physiological processing increasing/decreasing in one condition relative to another condition

semantic dementia

progressive loss of semanticc memory - conceptual knowledge of people, places and meanings

visual agnosia

impairment of deriving the meaning of a visually presented stimulus

prosopagnosia

inability to recognize familiar faces, lesion of right hemisphere is necessairy and sufficient for aquired prosopagnosia

transcranial magnetic stimulation (TMS)

noninvasive stimulation of brain caused by magnetic induction from a rapidly changing electrical current in a coil held over scalp. produced virtual lesions

transcranial electrical stimulation (TES)

noninvasive stimulation of the brain caused by passing a weak electrical current through it

strokes

disruption of blood supply to brain

aneurysm

overelastic region of artery prone to rupture

single dissociation

an aquired deficit affecting one area or task and sparing another

task demand artifact

one task performed sub-optimally.

reduced by repeating and clear instructions

task resource artifact

share same neural/cognitive resource but one task uses it more, leading to damage to this task

double dissociation

two single dissociations with complementary profiles

transperancy assumption

lesions affect one or more existing componants in the prexisting cognitivesystem but dont result in an entirely new cognitive system being made

diaschisis

a discrete brain region can disrupt functioning of distant brain regions that are structually intactttr

transcranial direct current stimulation (tDCS)

noninvasive stimualtion of the brain caused by passing a weak electrical direct current through it

transcranial altering current stimulation (tACS)

nonincasive stimulation of the brain caused by passing a weak alternating electrical current through it

transcranial random noise stimulation (tRNS)

noninvansive stimulation of the brain caused by passing weak electrical current through it, which fluctuates in direction and amplitude

cathodal tDCS

decreases cortisol excitability and performance

anodal tDCS

increase cortisol excitability and performancea

advantages of TMS

1. temporairy effects with no brain reorganisation
2. focal
3. lesions can be moved within subjects
4. can investigate functional intergration

challenges of TMS

cant stimulate some regions

minor discomfort

cannot be used with epilepsy patients

tDCS VS TMS

tDCS has poorer temporal and spatial resolution

tDCS can facilitate cognitive function through anodal tDCS

tDCS less discomfort

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single cell recordings

electrode placed in or near an electron (invasive) to measure the number of action potentials/spikes per second in response to a stimulus.

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very small electrode placed into axon (intercellular) or outside axon (extracellular)

electroencephalography and event related potentials - ERP

electrode placced on skull, measures summed electrical potentials from millions of neurons.

electroencephalography

often used for rhythmic ocillations, rate of ocillation dound to correlate with different behavioural activity.

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Measurement of electrical signals generated by the brain through externally placed electrodes

multicell recordings

the electrical activity of many individually recorded neurons recorded at one or more electrodes

grandmother cell

a hypothetical neuron that just responds to one particular stimulus, maybe also to related stimuli.

fully distributed representation

all information of a stimulus/event is carried in all neurons of a population

sparce distributed representation

distributed representation where a small proportion of the neurons carry information about a stimulus

rate coding

all informational content of a neuron may relate to the number of action potentials per second

temporal coding

the synchrony of firing may be used by a population of neurons to code the same stimulus or event

plotting timing of maximum intensity (spikes) between action potentials

mental chronometry

the study of the time course of information processing in the human nervous system

additive factors method

a general method for dividing reaction times into different four stages

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1. encoding
2. comparing
3. deciding
4. responding

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associative priming

reaction times to X after being presented Y is quicker if X and Y have been previously associated

event related potentials

the average amount of change in voltage at the scalp is linked to timing of particular cognitive events

measures reaction time

poor spatial resolution

dipole

a pair of positive and negative electrical charges seperated by a small distance

exogenous

related to properties of stimulus

endogenous

related to properties of task

inverse problem

difficulty of locating sources of electrical activity from measurements taken at scalp

dipole modelling

an attempt to solve the inverse problem in ERP research that involves assuming how many dipoles contribute to signal recorded at scalp

magnetoencephalography MEG

magnetic rather than electrical signals

more sensitive to activity at sulci

potentially good spatial resolution however very expensive