Lecture 3 part 2 - notes PDF

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Beyond Primary Visual Cortex • •

MT+ or V5 is an area of the brain that is particularly sensitive to motion Area MT in monkey has columns of cells that respond to motion in a specific direction.

Interfered with processing of small number of neurons in v5 MT – experiment was dots moving in random directions – trial where dots are moving in random directions and the monkey will say half of the time dots going to the left or the right – if make dots move to the right/left the monkey will say right/left – green line. Interfere with processing of neurons in brain – find neurons that are in a column that respond to left motion – give them extra stimulation – monkey increases responses to the left even if the dots are moving equally to left and right = black line. Link between directionally preference neurons and behaviour Allocate a lot of our brain to processing faces. Early on in neuroimagining – found that particular regions of the brain were specifically responsive to faces. Response in blue shows activity that occurs in region of brain when a face is presented. Particular area of brain is showing a preference to faces Different types of stimuli presented – shown in yellow – houses and red – faces and blue – chairs. Object category = different areas prefer different objects. Show participant nothing and asking them to imagine house/face/chair – the same network in brain is active – not perfect overlap but just thinking about objects – can see in the brain what the participant was thinking about - mindreading. Pinna = funnel sound waves to hit the tympanic membrane. Tympanic membrane vibrates. Acute levers = malleus, incus and stapes – they add leverage – mechanical advantage – vibration on tympanic membrane are strengthened when hit window at end of cochlea – this is all mechanic. Vibrations travel down the cochlea – in the cochlea is the nerve cells that detect vibration. First diagram= The inner ear is a boney structure. Labyrinth – maze of tunnels – give you balance. Second diagram =The spiraled up cochlea and if take a cross section of cochlea – key structures are tectorial membrane and basilar membrane – end up hair cells in between the 2 structures and they detect the deflections of the tectorial membrane. Relative change in position of the 2 membranes that generate deflection of the hair cells – when the hairs are deflected – pattern of the lid coming of a bin – ion channel allowing selective transport of potassium ions – resting potential would be negative – depolarises and has secondary effect of voltage gated calcium channels which will deplorise the cell further and end up with releasing neural transmitter at the synpase between hair cell and spiral ganglion neurite Unrolled the cochlea and seeing different potentials along basilar membrane – sound vibrations that impinge on window will get a diff distance around cochlea depending on frequency because of the basilar and tectoral membrane having diff properties as go along it

Basilar membrane – stiff and narrow near window so will take very high vibrations to displace it and low frequency vibrations wont have much effect. End – wide and floppy – slow and low frequency will generate the displacements. Along length of cochlea have a whole range of frequencies that you can hear....