3 - conceptual issues + methodologies

define memory

concept linking experience to subsequent responses to the environment
(neuroscientists try to then link physical properties to memory)

what are the criticisms of the LTP experiment to understand memory?

experiment is very artificial (electrical event, preparation of brain tissue)

unlikely to replicate actual behavioural experiences “unnatural stimulus delivered to an abnormal neural preparation”

HOWEVER. LTP studies do help with forming hypotheses!

training and test phase of memory

two phases are observable but the memory trace is not!

factors affecting behaviour

sensory

attentional

perceptual

motivational

emotional

motor

memory

learning performance distinction

eliminating other factors that affect performance (ex. motivation and motor abilities) to determine the manipulation’s actual effect on memory/learning.

short term memory

rapid decay

vulnerable to disruption

active

long term memory

slow decay

less vulnerable to disruption

inactive state

explanation for limited retrograde amnesia

causal event (head trauma) affected only active STM. interrupts consolidation

electroconvulsive shock (and memory disruption)

previously used with psychiatric patients memory loss

tried to use to cause amnesia in animals. not super successful

2 reasons for memory disruption

storage failure
retrieval failure

storage failure

interferes with processes responsible for storing the memory (consolidation)

permanent

retrieval failure

disrupts neural pathways that enable memory retrieval.
temporary (like forgetfulness)
(however, impossible to disprove.)

4 behavioural test methods

inhibitory avoidance conditioning
fear conditioning
spatial learning
recognition memory task

methods for manipulating brain function

stereotaxic surgery

genetic engineering

stereotaxic surgery

coordinate system on brain, targeting a spot w electrode/electrical current/cannula
can target sections for lesions, injections or implantations

conditional knockout methodology

turn off particular gene in a brain region (can also turn back on).

viral vector methodology

using viruses to deliver new genetic material into cells
replacing some of viral genome with desired material + elements that control gene expression (promotor sequence)

green fluorescent protein

used in viral vectors (coded to be translated) and is fluorescent to be easily identifiable

optogenetics

using light to regulate ion flow (using opsins)

fast acting

channelrhodopsin

used in optogenetics
sensitive to blue light
let Na+ into cell. (depolarization)

halorhodopsin

used in optogenetics sensitive to green light let Cl in

DREADD

designer receptor exclusively activated by designer drugs

viral vector introduces receptor, can choose to active using a synthetic ligand 🙂

gradual time scale

how do we categorize memory traces?

3 dimensions: duration, state, vulnerability to disruption

Neuroimaging, 2 categories

structural and functional

examples of structural neuroimaging

MRI, CT

examples of functional neuroimaging

fMRI, PET, EEG