seeing motion : from neural circuits to perceptual decisions

Seeing motion :

From neural circuits to perceptual decisions

From D. Hubel, 1995

From D. Hubel, 1995

From D. Hubel, 1995

From D. Hubel, 1995

From D. Hubel, 1995

From D. Hubel, 1995

Where do we go from here???

Sensory representation of motion

Pre-oculomotor circuitry

Oculomotor circuitry

Abstract decision representation??

??

??

An Eye Movement Matching Task

An Eye Movement Matching Task

An Eye Movement Matching Task

An Eye Movement Matching Task

An Eye Movement Matching Task

An Eye Movement Matching Task

10 sec 30 sec

independent, Poisson processes

(constant rate)

30 sec 10 sec

An Eye Movement Matching Task

Matching:response ratio= reward ratio

10 sec 30 sec

independent, Poisson processes

(constant rate)

30 sec 10 sec

25% 75%

An Eye Movement Matching Task

Matching:response ratio= reward ratio

frequentunsignaled changes in reward ratio

10 sec 30 sec

independent, Poisson processes

(constant rate)

30 sec 10 sec

25% 75%

An Eye Movement Matching Task

1:1

1:3

3:1

1:1

1:6

6:1

Crosscorrelograms

CorrelationCoefficient

Lead (responses)

“Experienced value” (EV) =

(weighting function) X (reward history)

Area LIP in the Macaque Brain

http://www.loni.ucla.edu/data/monkey

LIP

Time (msec)

Resp

onse

(p

eak

norm

aliz

ed)

Targ on Sac

Firing rate is related to experienced value (n=21)

0 200 400 600 0-200-400-6000

0.2

0.4

0.6

0.8

2. EV is represented in LIP, and the effects are often as large as those of the eye movement itself. EV is NOT computed in LIP.

Conclusions - Experienced Value (EV)

1. Under our conditions, EV is computed within a relatively short time window, extending no more than 5-10 trials into the past.

3. At least one of these brain structures (area LIP) represents additional decision variables such as the previously experienced value of alternative actions.

General Conclusions

1. We have established a causal relationship between the sensory representation of motion direction in the cortex and perceptual judgments of motion.

2. Candidate neural correlates of the decision process exist in at least three pre-oculomotor areas of the frontal lobe, parietal lobe and the upper midbrain. Causality is not yet established between these neural circuits and behavioral decisions. (We’re working on it!)

Indeed there are now no logical (and I believe no Insurmountable technical) barriers to the direct study of

the entire chain of neural events that lead from the initial central representation of sensory stimuli, through the many sequential and parallel transformations of those

neural images, to the detection and discriminationprocesses themselves, and to the formation of general

commands for behavioral responses and detailed instructions for their motor execution.

V . B . Mountcastle, Handbook of Physiology, 1985