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Title Temporal Processing in the Visual System
Publication Date
Date Available
Date Accessioned
Degree PhD
Discipline/Department Psychology
Degree Level doctoral
University/Publisher 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 \((\sim100 ms\) 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.


Subjects/Keywords Cognitive psychology; Neurosciences; LIP; Temporal Order Judgment; Temporal Processing; Time; Vision
Contributors 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)
Language en
Rights open
Country of Publication us
Record ID oai:dash.harvard.edu:1/10433469
Other Identifiers Aghdaee, Seyed Mehdi. 2013. Temporal Processing in the Visual System. Doctoral dissertation, Harvard University.
Repository harvard
Date Indexed 2018-02-26

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Temporal Order Judgment Reporting the perceived order of two stimuli is referred to as Temporal Order Judgment (TOJ). Experiments involving judgments of temporal order (or simultaneity) have been historically used to study problems in…

…stimulus. Davis and colleagues asked subjects to perform a temporal order judgment vs. shape judgment task of two stimuli (one in each visual hemifield), with the difficulty equated between the two tasks (Davis, Christie, & Rorden, 2009)…

…17470218.2010.495783 Woo, S. H., Kim, K. H., & Lee, K. M. (2009). The role of the right posterior parietal cortex in temporal order judgment. Brain Cogn, 69(2), 337-343. doi: 10.1016/j.bandc.2008.08.006 Yamada, J., & Noda, H. (1987)…

…List of Figures -------Chapter 2--------------Figure 1: Schematic of the phase judgment task….………………..……………………33 Figure 2: Thresholds for the phase judgment task………………………………………36 -------Chapter 3--------------Figure 3: Schematic of the temporal

order judgment (TOJ) task………………………..56 Figure 4: Behavioral data, single session examples & population………………………65 Figure 5: Single unit examples with different surround modulation effects………….....68 Figure 6: Single unit examples, SOA= 0 ms…

…occur within the membrane time constant of single neurons in the auditory brainstem (Carr & Konishi, 1990). On the other hand, we also make explicit judgments of relative timing. Explicit judgments of temporal order are crucial for many higher…

…That is, if we perceive event B as following event A, it is plausible that A is the cause of B; however, the reverse cannot to true. Thus determining the order of temporal events influences how we establish causal inferences between events. Compared to…

…implicit relative timing, we can determine explicit temporal order over much wider ranges of intervening intervals between events. " 1" 1.2 Where is “when” in the brain? Traditionally the basal ganglia and cerebellum have been implicated in…