Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for +publisher:"Harvard University" +contributor:("Cook, Erik"). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


Harvard University

1. Smolyanskaya, Alexandra. Dynamics of Cortical Decision Circuits during Changes in the Fidelity of Sensory Representations.

Degree: PhD, Neurobiology, 2012, Harvard University

Every waking moment, we make decisions, from where to move our eyes to what to eat for dinner. The ease and speed with which we do this belie the complexity of the underlying neuronal processing. In the visual system, every scene is processed via a complicated network of neurons that extends from the retina through multiple areas in the visual cortex. Each decision requires rapid coordination of signals from the relevant neurons. Deficits in this integration are likely causes of debilitating learning disorders, yet we know little about the processes involved. Previous studies of the macaque visual cortex indicate that as monkeys learn a new task the parts of the brain involved in decision making select which neurons they “listen to”: the most informative neurons become more strongly associated with the animal’s decisions as it learns. However, this process has only been studied over the course of several months as monkeys gradually learn a complex task. We set out to probe the dynamics of this relationship on a shorter timescale. We studied the middle temporal area (MT) of the visual cortex, where neurons are selective for binocular disparity (a depth cue) and motion direction; they have also been shown to contribute to perceptual decisions during motion- and depth-based tasks. After training monkeys on motion and depth detection tasks, we degraded the sensitivity of MT neurons for depth more than motion by reversibly inactivating two major inputs to MT—visual areas V2 and V3—by cooling. We hypothesized that degrading depth information more than motion would lead to bigger changes in the extent to which MT neurons contributed to decisions during the depth task than the motion task. We monitored this contribution to decisions, as measured by detect probability (DP), prior to and during daily inactivation sessions. We found that neuronal DP decreased during the depth task, indicating that neurons became less involved in these decisions. DP did not change during the motion task, suggesting that these changes can be specific to one feature. Our results revealed a level of fast, selective flexibility in the decision circuitry. Advisors/Committee Members: Born, Richard Todd (advisor), Maunsell, John (committee member), Wilson, Rachel (committee member), Kreiman, Gabriel (committee member), Cook, Erik (committee member).

Subjects/Keywords: cortex; inactivation; macaque; MT; vision; neurosciences; decision making

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Smolyanskaya, A. (2012). Dynamics of Cortical Decision Circuits during Changes in the Fidelity of Sensory Representations. (Doctoral Dissertation). Harvard University. Retrieved from http://nrs.harvard.edu/urn-3:HUL.InstRepos:9795731

Chicago Manual of Style (16th Edition):

Smolyanskaya, Alexandra. “Dynamics of Cortical Decision Circuits during Changes in the Fidelity of Sensory Representations.” 2012. Doctoral Dissertation, Harvard University. Accessed September 27, 2020. http://nrs.harvard.edu/urn-3:HUL.InstRepos:9795731.

MLA Handbook (7th Edition):

Smolyanskaya, Alexandra. “Dynamics of Cortical Decision Circuits during Changes in the Fidelity of Sensory Representations.” 2012. Web. 27 Sep 2020.

Vancouver:

Smolyanskaya A. Dynamics of Cortical Decision Circuits during Changes in the Fidelity of Sensory Representations. [Internet] [Doctoral dissertation]. Harvard University; 2012. [cited 2020 Sep 27]. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:9795731.

Council of Science Editors:

Smolyanskaya A. Dynamics of Cortical Decision Circuits during Changes in the Fidelity of Sensory Representations. [Doctoral Dissertation]. Harvard University; 2012. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:9795731

2. Aghdaee, Seyed Mehdi. Temporal Processing in the Visual System.

Degree: PhD, Psychology, 2012, Harvard University

Encoding time is one of the most important features of the mammalian brain. The visual system, comprising almost half of the brain is of no exception. Time processing enables us to make goal-directed behavior in the optimum “time window” and launch a ballistic eye movement, reach/grasp an object or direct our processing resources (attention) from one point of interest to another. In addition, encoding time is critical for higher cognitive functions, enabling us to make causal inferences. The limitations of temporal individuation in the visual stream seem to vary across the visual field: the resolution gradually drops as objects become farther away from the center of gaze, where little differences were found in terms of resolution for objects in the upper versus lower visual field. This resolution of temporal individuation is vastly different from the resolution ascribed to spatial individuation. If individuation is mediated through attention, as some researchers have proposed, the general term ”attention” seems to possess different properties, at least regarding temporal and spatial processing. Next we looked at another aspect of encoding time: Temporal Order Judgments (TOJ), where animals had to judge the relative timing onset of two visual events. After training two monkeys on the task, we recorded from neurons in the lateral intraparietal area (LIP), while the animals reported the perceived order of two visual stimuli. We found that LIP neurons show differential activity based on the animal’s perceptual choice: when the animal reports the stimulus inside the receptive field of the neuron as first, the cells show an increased level of activity compared to when the animal reports he same stimulus as second. This differential activity was most reliable in the tonic period of the response ((∼100 ms) after stimulus onset). However, no difference in visual response latencies was observed between the different perceptual choices. The parietal cortex has previously been implicated in temporal processing based on patient studies as well as neuroimaging investigations. Physiological studies have also suggested the involvement of parietal area in encoding elapsed time. However, our study is the first to demonstrate parietal neurons encoding relative timing.

Psychology

Advisors/Committee Members: Assad, John Abraham (advisor), Nakayama, Ken (committee member), Cavanagh, Patrick (committee member), Assad, John (committee member), Maunsell, John (committee member), Born, Richard (committee member), Cook, Erik (committee member).

Subjects/Keywords: Cognitive psychology; Neurosciences; LIP; Temporal Order Judgment; Temporal Processing; Time; Vision

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Aghdaee, S. M. (2012). Temporal Processing in the Visual System. (Doctoral Dissertation). Harvard University. Retrieved from http://nrs.harvard.edu/urn-3:HUL.InstRepos:10433469

Chicago Manual of Style (16th Edition):

Aghdaee, Seyed Mehdi. “Temporal Processing in the Visual System.” 2012. Doctoral Dissertation, Harvard University. Accessed September 27, 2020. http://nrs.harvard.edu/urn-3:HUL.InstRepos:10433469.

MLA Handbook (7th Edition):

Aghdaee, Seyed Mehdi. “Temporal Processing in the Visual System.” 2012. Web. 27 Sep 2020.

Vancouver:

Aghdaee SM. Temporal Processing in the Visual System. [Internet] [Doctoral dissertation]. Harvard University; 2012. [cited 2020 Sep 27]. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10433469.

Council of Science Editors:

Aghdaee SM. Temporal Processing in the Visual System. [Doctoral Dissertation]. Harvard University; 2012. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10433469

.