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You searched for +publisher:"Harvard University" +contributor:("Born, Richard T."). Showing records 1 – 3 of 3 total matches.

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Harvard University

1. Luo, Zhihao. Dissociating Components of Visuo-Spatial Attention.

Degree: 2016, Harvard University

Neuronal signals related to visuo-spatial attention are found in widespread brain regions, and these signals are generally assumed to participate in a common mechanism of attention. However, the effects of visuo-spatial attention on the behavioral performance of human and animal observers can be separated into two distinct components. When a subject directs its attention to a visual location, the subject can change either its criterion or its sensitivity between the attended and unattended locations. I first found that when monkeys are trained to do a variant of the Posner attention paradigm, a task used in many single-neuron studies of visuo-spatial attention, enhanced performance is typically associated with both changes in the subject’s criterion and changes in its sensitivity. This finding indicates that the neuronal modulations attributed to visuo-spatial attention in previous studies could be associated with a behavioral change in sensitivity, a change in criterion, or a combination of both. To measure how neuronal signals across the brain are associated with the two components of attention, I designed a task to isolate attentional changes in either the criterion or the sensitivity of the subject. While monkeys were performing this task, I recorded from area V4 of their visual cortex and found that attention-related neuronal modulations in V4 corresponded to behavioral changes in sensitivity, but not changes in criterion. Subsequently, I recorded from prefrontal cortex (areas 45 and 46) and found that unlike V4, visual responses in prefrontal cortex were modulated when either the animal’s sensitivity or its criterion was changed between visual locations. Either an enhancement in sensitivity or a liberal change in criterion was associated with an increase in the firing rates of visual neurons in prefrontal cortex. These findings show that attention-related neuronal signals across the brain are not equivalent in their contribution to the mechanisms of visuo-spatial attention. Neuronal modulations in prefrontal cortex contribute to behavioral changes in both criterion and sensitivity, while modulations in visual cortex contribute to only changes in sensitivity. The results indicate that visuo-spatial attention is not a single neurobiological process but instead consists of at least two separable mechanisms mediated by overlapping groups of brain structures.

Medical Sciences

attention; neurophysiology; V4; prefrontal cortex; signal detection theory

Advisors/Committee Members: Born, Richard T., Maunsell, John H., Assad, John, Lee, Daeyeol, Livingstone, Margaret.

Subjects/Keywords: Biology; Neuroscience

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

APA (6th Edition):

Luo, Z. (2016). Dissociating Components of Visuo-Spatial Attention. (Thesis). Harvard University. Retrieved from http://nrs.harvard.edu/urn-3:HUL.InstRepos:37944942

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Luo, Zhihao. “Dissociating Components of Visuo-Spatial Attention.” 2016. Thesis, Harvard University. Accessed October 24, 2020. http://nrs.harvard.edu/urn-3:HUL.InstRepos:37944942.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Luo, Zhihao. “Dissociating Components of Visuo-Spatial Attention.” 2016. Web. 24 Oct 2020.

Vancouver:

Luo Z. Dissociating Components of Visuo-Spatial Attention. [Internet] [Thesis]. Harvard University; 2016. [cited 2020 Oct 24]. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:37944942.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Luo Z. Dissociating Components of Visuo-Spatial Attention. [Thesis]. Harvard University; 2016. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:37944942

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Krieger, Brenna M. Predicting the Electrophysiological Responses of Murine Alpha Retinal Ganglion Cells to Artificial and Natural Visual Stimuli.

Degree: PhD, 2015, Harvard University

The retina sends many parallel channels of visual information to the brain through the axons of >20 retinal ganglion cell (RGC) populations. The purpose of these distinct circuits for vision remains an open question. Recent results suggest that each cell type responds selectively to a specific feature of the visual scene. These conclusions are derived primarily from experiments with artificial visual stimuli. It is unknown whether the insights gathered under such conditions extend to the natural environment in which the retina evolved. One can address this question by building a mathematical model of RGC responses to artificial stimuli and then testing how well that same model performs with natural visual input. For several RGC types this exercise has failed dramatically, indicating an imperfect understanding of their neural code. Here we focus on the mouse alpha RGCs, which possess large cell bodies, stout axons, and wide receptive fields. Three subtypes had been previously defined based on their responses to light steps: On-Sustained, Off-Sustained, and Off-Transient. We targeted these RGCs for recording using a transgenic mouse line in which GFP is expressed in all alpha subtypes. Quantitative analysis of the recorded light responses revealed four distinct physiological cell types: an On-Transient alpha RGC in addition to the other three type previously identified. Using both artificial stimuli and natural movies, we measured the visual responses of the mouse alpha cells. We then constructed a simple cascade-style model to link the stimulus to the firing rate. Based on electrophysiological recording and modeling, we found the visual messages the four alpha RGCs send to the brain to be similar in that they are minimally processed versions of the visual scene. Spatial averaging minimally influenced the responses of the alpha RGCs to the natural movies. Additionally, a simple linear- nonlinear model accounted very well for the visual responses of all four alpha RGC subtypes, correctly predicting at least 70% of the variance in firing. The same model worked for both artificial stimuli (e.g. random flicker) and natural stimuli (mouse-cam and simulated-mouse movies). This successful account of alpha cell function will be valuable as a retina model for understanding cortical vision in the behaving mouse. Advisors/Committee Members: Born, Richard T. (committee member), Cox, David D. (committee member), Hogle, James M. (committee member).

Subjects/Keywords: Biophysics, General; Biology, Neuroscience

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

APA (6th Edition):

Krieger, B. M. (2015). Predicting the Electrophysiological Responses of Murine Alpha Retinal Ganglion Cells to Artificial and Natural Visual Stimuli. (Doctoral Dissertation). Harvard University. Retrieved from http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226061

Chicago Manual of Style (16th Edition):

Krieger, Brenna M. “Predicting the Electrophysiological Responses of Murine Alpha Retinal Ganglion Cells to Artificial and Natural Visual Stimuli.” 2015. Doctoral Dissertation, Harvard University. Accessed October 24, 2020. http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226061.

MLA Handbook (7th Edition):

Krieger, Brenna M. “Predicting the Electrophysiological Responses of Murine Alpha Retinal Ganglion Cells to Artificial and Natural Visual Stimuli.” 2015. Web. 24 Oct 2020.

Vancouver:

Krieger BM. Predicting the Electrophysiological Responses of Murine Alpha Retinal Ganglion Cells to Artificial and Natural Visual Stimuli. [Internet] [Doctoral dissertation]. Harvard University; 2015. [cited 2020 Oct 24]. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226061.

Council of Science Editors:

Krieger BM. Predicting the Electrophysiological Responses of Murine Alpha Retinal Ganglion Cells to Artificial and Natural Visual Stimuli. [Doctoral Dissertation]. Harvard University; 2015. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:14226061

3. MANDELBAUM, GIL. Basal Ganglia Circuitry Controlling Action Selection.

Degree: PhD, 2019, Harvard University

A central goal of neuroscience is to understand how brain circuits integrate diverse streams of information, in order to make optimal future choices. The process of choosing an action, in vertebrate animals, crucially depends on the proper function of the basal ganglia (BG) circuits. However, the precise connectivity in the BG nuclei, as well as the activity patterns that underlie their function in action selection, are currently not well understood. To understand this, one must first identify the functional building blocks of the BG circuits. To this end, we dissected the circuitry of the thalamic Parafascicular Nucleus (PF), an excitatory input to the BG that is omitted from the majority of BG circuit function models. We found that, in mice, PF forms the densest subcortical projection to the striatum. This projection arises from transcriptionally and physiologically distinct classes of PF neurons, which are reciprocally connected with functionally-distinct cortical regions, differentially innervate striatum neurons, and are not synaptically connected in PF. Thus, mouse PF contains heterogeneous neurons that are organized into parallel and independent associative, limbic, and motor circuits. Furthermore, these subcircuits share motifs of cortical-PF-cortical and cortical-PF-striatum organization that allow each PF subregion, via its precise connectivity with cortex, to coordinate diverse inputs to striatum. In order to understand the functional consequences of this circuit organization, we designed a behavioral task in which mice were required to base their next choice on their previous actions and outcomes associations (AOA) in addition to software and hardware for rapid closed-loop optogenetic manipulations triggered off of specific task and behavioral parameters. Optogenetic stimulation of dorsal lateral STR direct and indirect spiny projection neurons during the AOA formation period caused biases in action choice made several seconds later, contraversive and ipsiversive, respectively. Similarly, stimulation during the delay period after the AOA had been formed but prior to reporting the choice caused the same bias. These data suggest that the execution of actions and reinforcement are linked through the dorsolateral striatum. We now seek to further establish this by silencing and recording activity patterns in the PF, STR, and CTX.

Medical Sciences

Advisors/Committee Members: Assad, John A. (advisor), Wilson, Rachel I. (committee member), Born, Richard T. (committee member), Costa, Rui M. (committee member).

Subjects/Keywords: Basal Ganglia; Circuits; Choice

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

APA (6th Edition):

MANDELBAUM, G. (2019). Basal Ganglia Circuitry Controlling Action Selection. (Doctoral Dissertation). Harvard University. Retrieved from http://nrs.harvard.edu/urn-3:HUL.InstRepos:41121319

Chicago Manual of Style (16th Edition):

MANDELBAUM, GIL. “Basal Ganglia Circuitry Controlling Action Selection.” 2019. Doctoral Dissertation, Harvard University. Accessed October 24, 2020. http://nrs.harvard.edu/urn-3:HUL.InstRepos:41121319.

MLA Handbook (7th Edition):

MANDELBAUM, GIL. “Basal Ganglia Circuitry Controlling Action Selection.” 2019. Web. 24 Oct 2020.

Vancouver:

MANDELBAUM G. Basal Ganglia Circuitry Controlling Action Selection. [Internet] [Doctoral dissertation]. Harvard University; 2019. [cited 2020 Oct 24]. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:41121319.

Council of Science Editors:

MANDELBAUM G. Basal Ganglia Circuitry Controlling Action Selection. [Doctoral Dissertation]. Harvard University; 2019. Available from: http://nrs.harvard.edu/urn-3:HUL.InstRepos:41121319

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