Neuroscience Lesson 3: Tools and Methods for Exploring the Brain's Information Processing, Lecture notes of Psychology

Download Neuroscience Lesson 3: Tools and Methods for Exploring the Brain's Information Processing and more Lecture notes Psychology in PDF only on Docsity! Tools and Methods of Neuroscience Lesson 3 (REACH Psychology, week 3) In this lesson ● Intro: how the brain receives sensory information ● Smallest scale: single cell recordings ● Temporal resolution: EEG + MEG ● Spatial precision: fMRI Proof- Auditory processing ● Fluid in the cochlea moves when pressure is applied ● Causes the Basilar Membrane to respond in a bell-like manner ● From base to apex - different frequencies ● Acts like a filter Filtering the information Filtering sensory information ● Sensory and motor information is transformed into a neuronal code ● Neuronal code (what do you think that is?) ● To understand how the brain activity encodes information we must measure and relate it to external stimuli using imaging techniques Single cell recordings ● Grandmother cell hypothesis - Local representation Single cell recordings - How is this encoded? ● The amplitude of an action potential does not vary much ● But the number of action potentials per second varies for different neurons ● Information about the stimulus is encoded in this pattern of action potentials - spike trains ● Rate coding ● Temporal coding ● Difference? Will 000111000111 to mean something different from 001100110011? Average firing rate 6 spikes/10 ms Single cell recordings ● Implanting a small electrode into the neuron axon or the membrane ● Invasive ● Mostly animal research, basic processes ● Or humans with brain surgery ● Cannot measure non-invasively, the signal/noise ration is to weak (one neuron - 70mV) EEG - is a bit tricky EEG cap locations Event Related Potentials ● Activity is recorded every couple of milliseconds ● After the activity was measured and filtered (0.1-30Hz) we can now analyse it. ● We record simultaneously from all sights (high SNR) ● Too noisy - how do we detect stimulus-specific activity? ● Average over trial at a point of stimulus presentation ● Electrophysiological response to a specific stimulus or a category - ERP ERP - components ● ERPs consist of several peaks ● These peaks are thought to correspond to different stages of stimulus processing ● For example - auditory ERPs ● N100 P200, P300 different components of the same ERP ● Respond to different properties of the stimulus Magnetoencephalography (MEG) ● Recording the fluctuations of the magnetic field ● A recent technique (comparatively) ● Using SQUIDs to amplify the brain’s magnetic signals ● Requires shielding ● MEG is only sensitive to Tangential currents ● While EEG is sensitive to the radial currents ● Not sensitive to deep areas Magnetic resonance imaging ● One of the greatest advances in the medical history ● Peter Mansfield and Paul Lauterbur got a Nobel Prize for it in 2003 MRI physics ● Neurons don’t have an internal supply of energy - sugar, oxygen ● They need replenishing from blood ● The more they fire the more blood rushes in ● More activation = more oxygen consumption ● Hemoglobin has different magnetic properties in its oxygenated and deoxygenated forms ● It measures the inhomogeneities of the magnetic field caused by difference in oxygen levels increase/decrease MRI physics ● Human tissue is water based - has O2 molecules ● But the amount of O2 varies in each tissue type ● This fact is used in MRI ● Strong magnetic field is applied to the body ● Protons (hydrogen in water) have low mass and a weak magnetic field and are aligned randomly (F1) ● The strong magnetic field forces them to align with it (F2)