Indre Viskontas | University of San Francisco (original) (raw)

Papers by Indre Viskontas

Pseudoscience, 2018

While hosting a television show on the Oprah Winfrey Network, I had the opportunity to investigat... more While hosting a television show on the Oprah Winfrey Network, I had the opportunity to investigate 12 claims of miracles, experienced by a wide swath of Americans. This chapter is a summary of some of the takeaway lessons that I learned during that time, as I observed how extraordinary events can be interpreted as evidence for the existence of the supernatural. In particular, our drive to find meaning combined with a faulty memory system, a bias towards confirming our beliefs and our uncanny ability to pick out patterns make it difficult for us to change our minds even in the face of new and contradictory evidence.

Handbook of Clinical Neurology, 2008

Publisher Summary The chapter provides an overview of the cortical components of cognition and th... more Publisher Summary The chapter provides an overview of the cortical components of cognition and the functions they serve and explores the specific cognitive deficits that result from dysfunction in each of these systems. The majority of cognitive processing begins with the interpretation of incoming sensory information, and it is in these sensory processing systems that the segregation of information is most apparent. Many syndromes of cognitive dysfunction are easily understood in light of topographical organization. The visual system is most intensely studied, and provides the best example of cortical specialization. The chapter describes the cortical topography of visual processing, followed by a discussion of some of the other sensory modalities. Much of the power in cognitive capacities comes from ability to maintain sensory information over time (memory), to control processing of sensory information (attention), to focus behavior so that goals can be achieved efficiently without distraction (executive functions) and to attach value to information, tailoring actions accordingly (emotion and motivation).

Page 1. Chapter 13 fMRI of Memory Federica Agosta, Indre V. Viskontas, and Maria Luisa Gorno-Temp... more Page 1. Chapter 13 fMRI of Memory Federica Agosta, Indre V. Viskontas, and Maria Luisa Gorno-Tempini Summary Numerous fMRI studies have investigated the network of brain regions critical for memory. Whereas neuropsychological ...

PLOS ONE, 2015

We investigate the dynamic structure of human gaze and present an experimental study of the frequ... more We investigate the dynamic structure of human gaze and present an experimental study of the frequency components of the change in gaze position over time during free viewing of computer-generated fractal images. We show that changes in gaze position are scaleinvariant in time with statistical properties that are characteristic of a random walk process. We quantify and track changes in the temporal structure using a well-defined scaling parameter called the Hurst exponent, H. We find H is robust regardless of the spatial complexity generated by the fractal images. In addition, we find the Hurst exponent is invariant across all participants, including those with distinct changes to higher order visual processes due to neural degeneration. The value we find for H of 0.57 shows that the gaze dynamics during free viewing of fractal images are consistent with a random walk process with persistent movements. Our research suggests the human visual system may have a common strategy that drives the dynamics of human gaze during exploration.

Neuropsychologia, 2016

Associations between co-occurring stimuli are formed in the medial temporal lobe (MTL). Here, we ... more Associations between co-occurring stimuli are formed in the medial temporal lobe (MTL). Here, we recorded from 508 single and multi-units in the MTL while participants learned and retrieved associations between unfamiliar faces and unfamiliar scenes. Participant&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s memories for the face-scene pairs were later tested using cued recall and recognition tests. The results show that neurons in the parahippocampal cortex are most likely to respond with changes from baseline firing to these stimuli during both encoding and recognition, and this region showed the greatest proportion of cells showing differential responses depending on the phase of the task. Furthermore, we found that cells in the parahippocampal cortex that responded during both encoding and recognition were more likely to show decreases from baseline firing than cells that were only recruited during recognition, which were more likely to show increases in firing. Since all stimuli shown during recognition were familiar to the patients, these findings suggest that with familiarity, cell responses become more sharply tuned. No neurons in this region, however, were found to be affected by recombining face/scene pairs. Neurons in other MTL regions, particularly the hippocampus, were sensitive to stimulus configurations. Thus, the results support the idea that neurons in the parahippocampal cortex code for features of stimuli and neurons in the hippocampus are more likely to represent their specific configurations.

The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry, 2013

Disorders of the brain and its sensory organs have traditionally been associated with deficits in... more Disorders of the brain and its sensory organs have traditionally been associated with deficits in movement, perception, cognition, emotion, and behavior. It is increasingly evident, however, that positive phenomena may also occur in such conditions, with implications for the individual, science, medicine, and for society. This article provides a selective review of such positive phenomena--enhanced function after brain lesions, better-than-normal performance in people with sensory loss, creativity associated with neurological disease, and enhanced performance associated with aging. We propose that, akin to the well-established field of positive psychology and the emerging field of positive clinical psychology, the nascent fields of positive neurology and positive neuropsychology offer new avenues to understand brain-behavior relationships, with both theoretical and therapeutic implications.

Abstract Blair argues that fluid cognition is dissociable from general intelligence. We suggest t... more Abstract Blair argues that fluid cognition is dissociable from general intelligence. We suggest that a more complete understanding of this dissociation requires development of specific process models of the mechanisms underlying fluid cognition. Recent evidence indicates that relational integration and inhibitory control, both dependent on prefrontal cortex, are key component processes in tasks that require fluid cognition.

... The Creating Brain: The Neuroscience of Genius. Accession number;06A0717536. Title;The Creati... more ... The Creating Brain: The Neuroscience of Genius. Accession number;06A0717536. Title;The Creating Brain: The Neuroscience of Genius. Author;ANDREASEN NANCY C.( ...

Prior studies have used fMRI to measure the onset of neural activity from a stable baseline with ... more Prior studies have used fMRI to measure the onset of neural activity from a stable baseline with a temporal precision on the order of 100 msec. Many important neural processes, however, reveal themselves as increases in activity that lie on top of another neural response. We attempted to determine whether fMRI could measure the timing of an increase that occurred 200 msec after initial response. Subjects viewed stimuli from three conditions. In our baseline condition, a low contrast flickering checkerboard was presented for 600 msec. We added a 400 msec contrast increment to this stimulus either at a 200 msec delay or immediately upon stimulus presentation; thus in the delay condition the low contrast checkerboard increased its contrast after 200 msec and remained high contrast for 400 msec, while in the immediate condition a high contrast flickering checkerboard reduced its contrast after 400 msec and remained low for 200 msec. We acquired BOLD fMR images every 100 msec (TR) while ...

Thinking & Reasoning, 2005

Reasoning requires making inferences based on information gleaned from a set of relations. The re... more Reasoning requires making inferences based on information gleaned from a set of relations. The relational complexity of a problem increases with the number of relations that must be considered simultaneously to make a correct inference. Previous work (Viskontas, Morrison, Holyoak, Hummel, &amp;amp;amp;amp;amp; Knowlton, 2004) has shown that older adults have difficulty integrating multiple relations during analogical reasoning, especially when required

The Neuroscientist, 2013

The traditional view of nervous system function postulates that a lesion to the brain will usuall... more The traditional view of nervous system function postulates that a lesion to the brain will usually lead to a loss of function, that a second lesion will inevitably exacerbate the effects of the first lesion, that sensory loss will generally lead to impairment, and that aging is always associated with functional deficits. These assumptions, however, appear in some cases to be incorrect, with implications for our understanding of brain-behavior relations and also for therapeutic endeavors in clinical settings.

Hippocampus, 2009

Memories for certain events tend to linger in rich, vivid detail, and retrieval of these memories... more Memories for certain events tend to linger in rich, vivid detail, and retrieval of these memories includes a sense of re-experiencing the details of the event. Most events, however, are not retained in any detailed way for more than a few days. According to one theory, the hippocampus plays a specific role in supporting episodic retrieval, that is, the re-experiencing of an event as part of one's personal past. This theory predicts that as episodic memories fade over time and are reduced to feelings of familiarity, activity in the hippocampus should no longer be associated with retrieval. We used high-resolution functional imaging to explore neural activity in medial temporal lobe subregions while participants performed a recognition task at both a short (10-min) and long (1-week) study-test delay. For each recognized item, subjects made ''Remember/Know'' judgments, allowing us to distinguish between items that were consistently episodic across the two tests and items that were initially episodic, but later became merely familiar. Our results demonstrate that activity in the subiculum is specifically associated with episodic recollection. Overall, recollected items were associated with higher activity in the subiculum than other items. For transiently recollected items, there was a decrease in subicular activity across the 1week delay as memory faded from recollection to familiarity, whereas consistently recollected items were associated with enhanced subicular activity at both delays. These results provide evidence of a link between subicular activation and recollective experience. V

Psychology and Aging, 2004

The difficulty of reasoning tasks depends on their relational complexity, which increases with th... more The difficulty of reasoning tasks depends on their relational complexity, which increases with the number of relations that must be considered simultaneously to make an inference, and on the number of irrelevant items that must be inhibited. The authors examined the ability of younger and older adults to integrate multiple relations and inhibit irrelevant stimuli. Young adults performed well at all but the highest level of relational complexity, whereas older adults performed poorly even at a medium level of relational complexity, especially when irrelevant information was presented. Simulations based on a neurocomputational model of analogical reasoning, Learning and Inference with Schemas and Analogies (LISA), suggest that the observed decline in reasoning performance may be explained by a decline in attention and inhibitory functions in older adults.

Neuropsychology, 2011

Objective-Individuals with semantic dementia (SD) have impaired autobiographical memory (AM), but... more Objective-Individuals with semantic dementia (SD) have impaired autobiographical memory (AM), but the extent of the impairment has been controversial. According to one report , patient performance was better when visual cues were used instead of verbal cues; however, the visual cues used in that study (family photographs) provided more retrieval support than do the word cues that are typically used in AM studies. In the present study, we sought to disentangle the effects of retrieval support and cue modality.