PSYC 212 Lecture 4: PSYC 212 – Lecture 4 – January 23rd

• School: McGill University
• Department: Psychology
• Course: PSYC 212
• Professor: Mathieu Roy

Document Summary

Psyc 212 lecture 4 january 23rd. Transduction of light by photoreceptors: remember: photoreceptors in the retina hyperpolarize (instead of depolarize) when they are activated. Receptive fields and lateral inhibition: receptive field refers to the region on the retina in which the stimuli influence a (cid:374)eu(cid:396)o(cid:374)"s fi(cid:396)i(cid:374)g (cid:396)ate. Re(cid:272)epti(cid:448)e fields ha(cid:448)e a (cid:272)e(cid:374)t(cid:396)e-surround organization (1) on/ off. Ganglion cell will preferentially respond to stimuli that are bright in the middle, but dark in the surround, or (2) off/ on. The purpose of this organization is to increase contrast. Dark depolarizes (renders polarity more positive) surround cones. This amplifies the bipolar on cell activity, and subsequently retinal ganglion cell activity: on-centre bipolar cells reverse the sign of the photoreceptor (as seen previously). Off- (cid:272)e(cid:374)t(cid:396)e (cid:271)ipola(cid:396) (cid:272)ells do(cid:374)"t (cid:396)e(cid:448)e(cid:396)se the sig(cid:374) of the photo(cid:396)e(cid:272)epto(cid:396). This allo(cid:449)s (cid:271)la(cid:272)k-on- (cid:449)hite to (cid:862)sta(cid:374)d out(cid:863) as (cid:373)u(cid:272)h as (cid:449)hite-on-black.