seeing motion : from neural circuits to perceptual decisions
TRANSCRIPT
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
