Transcript Cognitive neuroscience lecture

Neuron Structure
Synapse
The Synapse
1. Synthesis of
neurotransmitter (NT)
2. Storage and transport
of NT within vesicles
3. NT Release
4. Activation of
postsynaptic receptors
5. Termination of
transmitter effect (e.g.
reuptake)
Resting Potential
Sodium ions are concentrated on the outside of
the axon membrane.
Potassium ions are concentrated on the inside
of the axon membrane.
Ion channels are closed.
The inside of the axon membrane is more
negative that is the outside.
Action Potential
• Action potential occurs when the membrane
potential rapidly shifts from -70 to +40 mV
– Ion channels open in the membrane, allowing sodium
ions to enter the axon
– Sodium entry shifts the membrane potential toward a
positive value
– Potential is restored when other channels open,
allowing potassium ions to exit the axon
Myelin
• Myelin is a fatty, waxy substance coating
the axon of some neurons.
• Functions:
– Speeds neurotransmission
– Insulates neurons from each other
– Makes neurotransmission more efficient
Neurotransmitters
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Serotonin
Acetylcholine
Dopamine
Norepinephrine
Epinephrine
GABA
Endorphins
Midline Brain View
Brainstem
• Brainstem is a primitive portion of brain
– Pons: involved in respiration, sleep
regulation, dreaming
– Medulla: involved in life support functions
such as respiration and heart rate
– Reticular activating system is an arousal
system within the brainstem
Subcortical Brain Areas
• Corpus callosum: band of axons that
interconnects the hemispheres
• Thalamus: sensory relay area
• Limbic system: involved in emotionality
• Hypothalamus: feeding, fleeing, mating,
fighting, homeostasis
• Cerebellum: involved in motor control
Limbic System: Seat of Motivation, Emotions
Cerebral Cortex
• Cortex refers to the outer covering of the brain
– Consists of left and right hemispheres
– Cortex is divided into lobes
• Frontal: Self-awareness, planning, voluntary movement,
emotional control, speech, working memory
• Parietal: Body sensations
• Occipital: Vision
• Temporal: Hearing, language comprehension
– Localization of function: do discrete circuits carry
out different functions?
Cortical Lobes
Cerebral Cortex
Motor and Somatosensory Cortex
Language areas: Broca & Wernicke
Primary Visual Pathways
Primary Visual Pathways
• Secondary
Visual
Pathways:
Dorsal and
Ventral
Streams
Dorsal and Ventral Visual Pathways
Auditory Pathways
LeDoux’s two pathways of emotion
Nee, et al., STM/LTM article
• Damage to
Medial
Temporal
produced LTM
deficits while
leaving STM in
tact. Inferior
Temporal = LT
visual pattern
recognition
deficits
Medial and Inferior Temporal lobes
Perisylvian cortex: STM disruptions
Behavioral data confirming STM/LTM
distinction
• Presentation rate affects primacy but not
recency effect
• Increased delay affects recency but not
primacy effect. (Glanzer & Cunitz, 1966)
• Med. Temporal activation for early probes
in serial recall paradigm
• R infer. parietal for late probes (Talmi,
Grady, Goshen-Gottstein, & Moscovitch
(2005)
STM/LTM distinction or novelty (MTL) and
resistance to distraction (frontal)
• Ranganath & Blumenfeld (2005) argue that MTL binds novel items
together in single representation. STM storage can be disrupted in
patients with MT damage when items are novel (novel items rarely
used in most STM studies)
• Furthermore patients with frontal damage can perform STM task
when distractions are minimized.
• Sakai, Rowe, & Passingham (2002), subject did STM spatial task –
found greater frontal activity on ‘correct’ trials, less on ‘error’ trials
suggesting frontal areas important for filtering distractions. Similar
findings for words and pseudo words.
• Other evidence suggesting that phonological deficits are found in
patients with perisylvian damage, thus this area may not be
specifically for STM, but may STM tasks may typically require
phonological rehearsal.
• STM is ‘attentionally mediated activation’ of LTM representations.
Episodic retrieval and STM retrieval
• Similar processes may exist in LTM, STM
processes.
• Cabeza, et al., 2002 – episodic retrieval:
Subs judge probe word as ‘remembered
from earlier list,’ ‘known’ or ‘not seen
before’. STM: yes/no to probe after study
• Same areas of left frontal active in both
cases. Anterior frontal may play a
monitoring role.