Neural correlates of prior expectations of motion in the lateral intraparietal and middle temporal areas.
ABSTRACT Successful decision making involves combining observations of the external world with prior knowledge. Recent studies suggest that neural activity in macaque lateral intraparietal area (LIP) provides a useful window into this process. This study examines how rapidly changing prior knowledge about an upcoming sensory stimulus influences the computations that convert sensory signals into plans for action. Two monkeys performed a cued direction discrimination task, in which an arrow cue presented at the start of each trial communicated the prior probability of the direction of stimulus motion. We hypothesized that the cue would either shift the initial level of LIP activity before sensory evidence arrived, or it would scale sensory responses according to the prior probability of each stimulus, manifesting as a change in slope of LIP firing rates. Neural recordings demonstrated a clear shift in the activity level of LIP neurons following the arrow cue, which persisted into the presentation of the motion stimulus. No significant change in slope of responses was observed, suggesting that sensory gain was not strongly modulated. To confirm the latter observation, middle temporal area (MT) neurons were recorded during a version of the cued direction discrimination task, and we found no change in MT responses resulting from the presentation of the directional cue. These results suggest that information about an immediately upcoming stimulus does not scale the sensory response, but rather changes the amount of evidence that must be accumulated to reach a decision in areas that are involved in planning action.
Full-textDOI: · Available from: Gregory C Deangelis, Jun 13, 2015
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ABSTRACT: Target detection performance is known to be influenced by events in the previous trials. It has not been clear, however, whether this bias effect is due to the previous sensory stimulus, motor response, or decision. Also it remains open whether or not the previous trial effect emerges via the same mechanism as the effect of knowledge about the target probability. In the present study, we asked normal human subjects to make a decision about the presence or absence of a visual target. We presented a pre-cue indicating the target probability before the stimulus, and also a decision-response mapping cue after the stimulus so as to tease apart the effect of decision from that of motor response. We found that the target detection performance was significantly affected by the probability cue in the current trial and also by the decision in the previous trial. While the information about the target probability modulated the decision criteria, the previous decision modulated the sensitivity to target-relevant sensory signals (d-prime). Using functional magnetic resonance imaging (fMRI), we also found that activation in the left intraparietal sulcus (IPS) was decreased when the probability cue indicated a high probability of the target. By contrast, activation in the right inferior frontal gyrus (IFG) was increased when the subjects made a target-present decision in the previous trial, but this change was observed specifically when the target was present in the current trial. Activation in these regions was associated with individual-difference in the decision computation parameters. We argue that the previous decision biases the target detection performance by modulating the processing of target-selective information, and this mechanism is distinct from modulation of decision criteria due to expectation of a target.Frontiers in Human Neuroscience 05/2015; 9. DOI:10.3389/fnhum.2015.00261 · 2.90 Impact Factor
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ABSTRACT: A recent line of work has found remarkable success in relating perceptual decision-making and the spiking activity in the macaque lateral intraparietal area (LIP). In this review, we focus on questions about the neural computations in LIP that are not answered by demonstrations of neural correlates of psychological processes. We highlight three areas of limitations in our current understanding of the precise neural computations that might underlie neural correlates of decisions: (1) empirical questions not yet answered by existing data; (2) implementation issues related to how neural circuits could actually implement the mechanisms suggested by both extracellular neurophysiology and psychophysics; and (3) ecological constraints related to the use of well-controlled laboratory tasks and whether they provide an accurate window on sensorimotor computation. These issues motivate the adoption of a more general "encoding-decoding framework" that will be fruitful for more detailed contemplation of how neural computations in LIP relate to the formation of perceptual decisions.Frontiers in Integrative Neuroscience 10/2012; 6:86. DOI:10.3389/fnint.2012.00086
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ABSTRACT: THE ABILITY OF SMOOTH PURSUIT EYE MOVEMENTS TO ANTICIPATE THE FUTURE MOTION OF TARGETS HAS BEEN KNOWN SINCE THE PIONEERING WORK OF DODGE, TRAVIS, AND FOX 1930 AND WESTHEIMER 1954 THIS ARTICLE REVIEWS ASPECTS OF ANTICIPATORY SMOOTH EYE MOVEMENTS, FOCUSING ON THE ROLES OF THE DIFFERENT INTERNAL OR EXTERNAL CUES THAT INITIATE ANTICIPATORY PURSUIT WE PRESENT NEW RESULTS SHOWING THAT THE ANTICIPATORY SMOOTH EYE MOVEMENTS EVOKED BY DIFFERENT CUES DIFFER SUBSTANTIALLY, EVEN WHEN THE CUES ARE EQUIVALENT IN THE INFORMATION CONVEYED ABOUT THE DIRECTION OF FUTURE TARGET MOTION CUES THAT CONVEY AN EASILY INTERPRETABLE VISUALIZATION OF THE MOTION PATH PRODUCE FASTER ANTICIPATORY SMOOTH EYE MOVEMENTS THAN THE OTHER CUES TESTED, INCLUDING SYMBOLS ASSOCIATED ARBITRARILY WITH THE PATH, AND THE SAME TARGET MOTION TESTED REPEATEDLY OVER A BLOCK OF TRIALS THE DIFFERENCES AMONG THE CUES MAY BE UNDERSTOOD WITHIN A COMMON PREDICTIVE FRAMEWORK IN WHICH THE CUES DIFFER IN THE LEVEL OF SUBJECTIVE CERTAINTY THEY PROVIDE ABOUT THE FUTURE PATH PURSUIT MAY BE DRIVEN BY A COMBINED SIGNAL IN WHICH IMMEDIATE SENSORY MOTION, AND THE PREDICTIONS ABOUT FUTURE MOTION GENERATED BY SETS OF CUES, ARE WEIGHTED ACCORDING TO THEIR RESPECTIVE LEVELS OF CERTAINTY ANTICIPATORY SMOOTH EYE MOVEMENTS, AN OVERT INDICATOR OF EXPECTATIONS AND PREDICTIONS, MAY NOT BE OPERATING IN ISOLATION, BUT MAY BE PART OF A GLOBAL PROCESS IN WHICH THE BRAIN ANALYZES AVAILABLE CUES, FORMULATES PREDICTIONS, AND USES THEM TO CONTROL PERCEPTUAL, MOTOR, AND COGNITIVE PROCESSES:Journal of Vision 05/2014; 14(5). DOI:10.1167/14.5.10 · 2.73 Impact Factor