PSYC211 Semester 2

central nervous system (CNS)

central nervous system (CNS)

encompasses the brain and the spinal cord, receives, processes and responds to sensory information

peripheral nervous system

nerves outside the brain and spinal cord. communication network between the CNS and the body. sensory and motor neurons.

somatic nervous system

division of the PNS that controls the bodies skeletal muscles

afferent

input to a nerve

efferent

output of a nerve

cranial nervess

12 pairs of nerves that carry messages to and from the brain

spinal nerves

21 pairs go in and out of the brain, come in through the dorsal (back) side and leave through the ventral (front) side

forebrain

telencephalon- cerebral cortex

diencephalon- subcortical

neurons

a nerve cell; the basic building block of the nervous system

neurons- voltage

have a negative membrane potential of -70mv while resting. flow of ions across the membrane cause changes in potential which creates an electrical impulse.

ions involved in action potential

sodium enters the cells, potassium leaves

sodium concentration

concentration gradient of sodium is into the cell

electrical gradient for sodium is also into the cell

action potential

rapid change in the voltage of the cell’s membrane, when action potential occurs the neuron is said to have fired.

graded potential

stimuli opening a gated channel causing a change in the membrane potential.

ESPS

Excitatory post-synaptic potential

Hodgkin-Huxley Cycle

describes how action potentials in neurons are initiated and propagated.

synaptic/receptor potential → initial depolarisation of membrane →opening of sodium channels → sodium flows into neuron

depolarisation

the change from a negative resting potential to a positive action potential

how many nerves are in the skull receiving or sending messages?

12

electrical gradient

unlike charges attract

concentration gradient

diffusion across a membrane

ion channels

voltage gated sodium channels. A certain voltage is required for them to open.

causes a positive feedback loop.

action potential propagation

travels along axon, at 0.5 to 2 meters per second

myelin

wraps around axons and speeds up action potential propagation. myelin acts as insulation and prevents the voltage channels from being operative in that region.

multiple sclerosis

myelin sheath destruction, causes a disruption in nerve impulse conduction

retina

groups of cells that are responsive to photons and light projected onto the retina.

rod

scoptic; important in low light. poor acuity achromatic vision in low light levels.

cone

photo-topic; high acuity colour vision in good illumination

fovea

where visual acuity is the highest “small pit”.

ipRGC

intrinsically photosensitive retinal ganglion cells, respond to light

synaptic transmission

one neuron communicates with another. a neurotransmitter is released from the pre-synaptic neuron. the neurotransmitter then binds to receptor causing an ion channel to open or close, the ions travel across a membrane changing electrical potential. (neuronal communication)

lateral inhibition

neurons response to a stimulus is inhibited by the excitation (applied energy to something) of a neighboring neuron

how many types of cones are there

3

opponent processes in motivation

approach, avoidance arises from competition between the drive to pursue reward and to avoid harm.

visual world maps onto the retina

objects on the left hand side of the visual field will be reflected onto the right side of the retina, the opposite is true for the right hand side of the visual field.

lateral geniculate nucleus

nucleus or sub area of the thalamus. visual cells in V-1 that respond to lines.

primary visual cortex

where 90% of visual information goes after LGN.

optic chiasm

the cross over from left visual field to the right side of the retina and the right visual field to the left side of the retina.

LGN retinotopic map

mapping from where the image falls on the retina is mapped within the lateral geniculate nucleus

simple cells

cells in V1 that respond to line, or gradient, orientated in particular direction

complex cells

cells in V1 that give best response to moving lines of a particular orientation. are orientation selective. nearly all binocular.

what is the difference between simple and complex cells?

complex cells are not binary, there is no, on/off area. where there is for simple cells.

process from visual field to retina

1. retinal ganglion cells

2. LGN

3. simple cells

4. complex cells

topographic organisation

information from the external world is mapped spatially in the brain

top-down processing

cortex makes assumptions about the environment and fills in gaps

bottom-up processing

analysis that begins with the sensory receptors and works up to the brains integration of sensory information.

V5 motion

ventral stream goes to V5. focuses on how an object is moving.

neurological evidence of V5

people with bilateral damage of V5 develop akinetopsia, the failure to perceive motion

sound pressure

waves in the air have repeating pressure pulses at particular frequencies and wavelengths. low frequency = waves further apart

pressure pulses

travel at 340 metres/second

humans can hear

20 to 20,000 Hz however we have age related hearing loss

hearing

Sound waves entering the outer ear then push on the ear drum of the middle ear which pulses the bones also in the middle ear. The bones press on the Cochlea which has a tectorial membrane that pushes up and down with the sound pulses which makes hair cells cilia move and down which opens the ion channels and allows the pressure waves to be turned into electrical signals. (The Organ of corti is just the combo of tectorial membrane, sensory hair cells and the basilar membrane).

cochlea

where sound information is received

hair cells

respond to movement, mechanical movement causes ion change and electrical impulses

transduction

sound frequency to spatial representation

McGurk effect

visual speech is affecting auditory speech. The way a person move’s their mouth effects the way they hear the auditory information.

dorsal stream

runs over the top of the cortex, uses visual information to guide the body. movements used for grasping a target.

ventral stream

identify what the objects are, shape, size and texture

Jennifer Aniston cells

certain cells respond to particular people/faces. individual cells that fire for specific people.

invariance

remaining unchanged regardless of the changes in the conditions of the measurements.

gnostic/grandmother cells

neuron which encodes and responds to a highly specific but complex stimulus e.g., grandmother

grandmother cell (local coding) theory

the coding in the nervous system in hierarchal and cells only fire when looking at specific stimulus.

problems with the local coding theory

1- requires a large number of grandmother cells, everything would have to be represented by a single cell.

2- susceptible to damage

3- how does one perceive novel objects

4- probability that you happen to come across the one cell that responds to a specific photo us extremely unlikely.

5-generalisation is difficult

6- pattern completion and generalisation requires access to representations of other similar objects.

Dense encoding theory

ensemble or population of cells that represent an image or idea. the representation is distributed across a number of cells, these cells are able to communicate with each other and the sum of activity creates representations.

dense encoding

• pattern completion and generalisation

• requires overlap between representations

• distributed representation

local encoding

• pattern separation

• requires separation of representations

• grandmother cells

• sparse encoding

distributed encoding

spread across many cells, all cells respond when you see an object

Doris Tsao- facial representation code

took a series of faces and deconstructed them into component parts. landmarks represent that face shape. found cells that seemed to respond to one of the particular features that seemed to make faces different in terms of shape and appearance.

convergent hierarchical coding

cells firing for each feature of an object converge on a common target cell that is representative of those collective feature. potentially faster but inflexible and hardwired, ineffective for coding modified or novel objects or experiences.

temporal binding

features that occur together in time are more likely to be related. distributed neural responses are tied together by the coordinated timing of their firing patterns. “cells that fire together, wire together”.

pareidolia

ambiguous information where the nervous system interprets something else.

multi-store model of memory

sensory memory > working memory > long-term memory (retrieval and rehearsal causes working memory to stay in long term memory).

Memory

each psychologically significant event, sensation, perception, expectation, memory or though is the result of a particular pattern of activity in a group of interconnected neurons (assembly).

Donald Hebb memory storing

long-term memory depends on changes in synaptic strength

how do synapses strengthen

when presynaptic and postsynaptic cells fire together (cells that fire together, wire together).

reactivation

patterns of neural activity are re-expressed when experiences are remembered.

fear induction

pain neurons firing at the same time as neurons representing visual stimuli creates fear,

long term potentiation (LTP)

synapses can be strengthened by artificial electrical stimulation. after LTP there is an increase in neural activity and more receptors are available. physical changes at the synapses are helping change the strength of the synapse.

why does LTP occur?

extra stimulation causes glutamate to bind to NMDA receptor and the ion channels associated opens and lets Mg2+ out and Ca2+ in

how to test LTP

rat in a pool tries to find platform. those with NMDA antagonist do much worse. over activation of LTP also confuses rats.

testing LTP against memory

• show that blocking LTP prevents memory formation

• show that reversal of LTP produces forgetting

• show that learning leads to LTP-like changes

• show that producing LPT creates false memories or masks existing memories.

NMDA

blocks receptors, high dosage blocks LTP

Morris water maze

test of memory in lab rodents. placing rodents in tank of water, animals work out the location of the pond. a day later take the platform out and see if the animal searches doe the quadrant where that platform was. disrupting LTP maintenance with ZIP produces forgetting.

equipotentiality

the idea that memory is distributed throughout the brain rather than confined to any specific location. Other parts of the brain can adapt if areas are damaged.

area V4

involved with storing colour

patient M.P. bilateral lesion of V5

difficulty with everyday tasks, no smooth movement akinetopsia

motion detection

• captures attention

• separates foreground and background

• helps compute the distance of various objects

• computes 3D shapes

binding

brain integrates activity (form, colour, size, orientation, texture, direction of movement).

Patient H.M.

removed hippocampus and amygdala to stop seizures. post surgery suffers anterograde amnesia. had intact short term memory but could not create new memories.

H.M. deficits showed us that…

• intelligence is not about having a good memory

• dissociation of declarative memory from working and procedural memory

• the hippocampus and rhinal cortex is involved in memory consolidation

patient RB

ischemic episode during open heart surgery. anterograde amnesia and very minor retrograde amnesia.

patient NA

had a mini fencing stick shoved up his nose. Anterograde amnesia and visual learning deficit.

Wernicke-Korsakoff syndrome

occurs in heavy drinkers, producing similar memory deficits to those that result from temporal lobe damage. result of lack of thiamine (vitamin B1). Damage to dorsomedial nucleus of the thalamus.

types of explicit memory

episodic and semantic

types of implicit memory

procedural, priming, conditioning, habituation

egocentric

represent space relative to our body or the individual (left/right)

allocentric

reference to the external world (North, South) relative to others.

beacon homing

travelling directly towards a fixed landmark, uses egocentric cues

path integration/dead reckoning

calculating one's current position by using a previously determined position, and advancing that position based on known or estimated speeds, elapsed time, and course

piloting

a type of navigation using landmarks relative distance

rat study water navigation

rats with hippocampal damage had issues with piloting, though they were fine when using beacon homing.