Memory, Brain (Chapter 8.1) Vengertsev Dmitry

Agenda Goals: 1) provide general overview of what we do know about underlying biological processes and brain structures that support memory 2) introduce difficulties in conducting this kind of research The Neuron The Brain Methods of Investigation the way memory stored in the brain

The Neuron Memory involves a persistent change in the relationship between neurons:  Structural modification  Biochemical events within neurons that change the way in which neighboring neurons communicate Squire, 1987

The Nervous system Glia cells (support, maintenance) Neurons – cells that process and transmit information  Sensory neurons (take information outside the system – light, touch…)  Motor neurons (provide instructions to muscles and affect glands)  Inter-neurons (majority) Simplified drawing:  Dendrites, Axon, Soma (cell body) Myelin sheath

Signal processing (1)

Signal processing (2) Synapse – gap between the end of the axon of one neuron and the dendrites of another Neurotransmitters – chemicals that transmit the neural impulse over synapse PSP – postsynaptic potential – change in membrane potential:  increase the likelihood that receiving neuron will process  remain or decrease action potential (in this case neurotransmitters are killed by enzymes)

The Brain Hindbrain (connect the brain and spinal cord, includes medulla, pons, cerebellum) Midbrain (between hindbrain and forebrain, includes tectum) Forebrain (includes thalamus, hypothalamus, cerebrum) Each cerebral hemisphere divided into four lobes: frontal, parietal, temporal and occipital

Methods of Investigation Invasive (involve damage to brain)  accidents  animal studies  recording from single neurons Noninvasive (little risk)  measuring blood flow, electrical activities at the brain,…

Invasive method Memory centered on the hippocampus. Hippocampus is responsible for getting together the contextual features of a situation and create a representation of every experience. Animal studies 1. Rats (have similar anatomy of hippocampus) 2. Monkeys (have similar brain structure) Micro-electrode implanted in the brain recorded activity of single group of neurons. Problems:  Generalizing from laboratory animals to human  How can be such complex system investigated if we make a hole in the center of it

Noninvasive methods (1) CT (computer tomography)  shows brain structure  measure difference in absorption of X-rays by tissues with different density PET (position emission tomography)  shows activity  neurons use glucose as a source of energy. Patient’s injected with radioactive glucose and do task MRI (magnetic resonance imaging)  shows brain structure  magnetic resonance

Noninvasive methods (2) functional MRI  MRI + tracking blood flow in the brain  the more active brain area is the more blood flows to it  produce picture of brain activity Electroencephalograms (EEGs)  measure pattern of electrical activity through electrodes attached to the scalp Event-related potentials (ERPs)  instantaneous changes in EEG associated with a presentation of particular stimulus

Noninvasive methods (3) Behavioral studies  Kinsbourne and Cook: compare performance on a balancing task when subject (right-handed person) either vocalize or remain silent  Results: right hand: better not to speak (reason: left hemisphere controls the right hand and also is the seat of language) left hand: speak! speak! (reason: verbalizing helped by distracting the subjects enough that they didn’t focus too much attention on balancing)

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