Biomedical subjects

Oshin Vartanian

Publications and source records attributed to Oshin Vartanian.

6 recordsLinked to original sources

PubMed2006

Hemispheric specialization in human prefrontal cortex for resolving certain and uncertain inferences.

Uncertainty is a fact of life that must be accommodated in real-world decision making. Although it has been suggested that the right prefrontal cortex (PFC) has a special role to play in decision making under uncertainty, there is very little hard data to support this hypothesis. To better understand the roles of left and right PFCs in reasoning and decision making in situations with complete and incomplete information, we administered simple inference problems to 18 patients with lateralized focal lesions to PFC (9 right hemisphere, 9 left hemisphere) and 22 age- and education-matched normal controls. The stimuli were systematically manipulated for completeness of information regarding the status of the conclusion. Our results demonstrated a 2-way interaction such that patients with left PFC lesions were selectively impaired in trials with complete information, whereas patients with right PFC lesions were selectively impaired in trials with incomplete information. These results provide compelling evidence for hemispheric specialization for reasoning in PFC and suggest that the right PFC has a critical role to play in reasoning about incompletely specified situations. We postulate this role involves the maintenance of ambiguous mental representations that temper premature overinterpretation by the left hemisphere.

Adult↗

PubMed2005

Task constraints modulate activation in right ventral lateral prefrontal cortex.

Lesion data suggest that right prefrontal cortex (PFC) plays a critical role in open-ended problem solving. To test this hypothesis, we scanned fifteen normal subjects with fMRI as they completed three types of anagram problems varying in the level of constraints placed on the search space. On unconstrained trials, they rearranged letters to generate solutions (e.g., Can you make a "Word with ZJAZ?"). On semantically constrained trials, they rearranged letters to generate solutions within particular semantic categories (e.g., Can you make a type of "Music with ZJAZ?"). On baseline trials, they rearranged letters to make specific words (e.g., Can you make the word "JAZZ with ZJAZ?"). As predicted, the critical comparison of unconstrained vs. semantically constrained trials revealed significant activation in right ventral lateral PFC, as well as left superior frontal gyrus, frontopolar cortex, right superior parietal lobe, right post central gyrus, and the occipital-parietal sulcus. Furthermore, activation in right ventral lateral PFC (BA 47) increased as the constraints placed on the anagram search space were reduced. We argue that the activation in right ventral lateral PFC is related to hypothesis generation in unconstrained settings, whereas activation in other structures is related to additional processes linked to anagram problems such as semantic retrieval, semantic categorization, and cognitive monitoring. These results extend the lesion data and imaging studies by demonstrating that a relative absence of constraints on the solution space is sufficient to engage right ventral lateral PFC in hypothesis generation tasks.

Adult↗

PubMed2005

The link between composition and balance in masterworks vs. paintings of lower artistic quality.

In painting, composition is commonly defined as the two-dimensional arrangement of elements within the canvas. Each element is considered to have a perceptual weight. The arrangement of these weighted elements determines how balanced a painting is. It has been suggested that due to superior composition, masterworks may be more balanced than works of lower artistic quality. We tested this hypothesis by instructing our participants to rate masterworks and selections of lower artistic quality on balance. This hypothesis was not supported. Second, it has been suggested that rearranging elements within a painting may have a more detrimental effect on composition (and by extension balance) in masterworks than in selections of lower artistic quality. This view associates works of higher artistic quality with visual rightness, thereby predicting that compositional change would be more likely to cause deviations from a visually right state in masterworks. We tested this hypothesis by displacing an element within each painting to a different location, and measuring the effect on balance. In accordance with recent findings in the literature, we also took into account the severity of the compositional alterations. The results demonstrated that compositional alteration affected balance ratings equally across masterworks and selections of lower artistic quality. These results demonstrate that, although balance is a function of compositional structure, balance on its own is not sufficient to distinguish between works of varying artistic quality. To the extent that balance is considered a function of composition, the results suggest that masterworks are distinguished from works of lower artistic quality for reasons other than solely composition.

Adult↗

PubMed2004

Dissociating the roles of right ventral lateral and dorsal lateral prefrontal cortex in generation and maintenance of hypotheses in set-shift problems.

Although patient data have traditionally implicated the left prefrontal cortex (PFC) in hypothesis generation, recent lesion data implicate right PFC in hypothesis generation tasks that involve set shifts (lateral transformations). To test the involvement of the right prefrontal cortex in a hypothesis generation task involving set shifts, we scanned 13 normal subjects with fMRI as they completed Match Problems (a classic divergent thinking task) and a baseline task. In Match Problems subjects determined the number of possible solutions for each trial. Successful solutions are indicative of set shifts. In the baseline condition subjects evaluated the accuracy of hypothetical solutions to match problems. A comparison of Match Problems versus baseline trials revealed activation in right ventral lateral PFC (BA 47) and left dorsal lateral PFC (BA 46). A further comparison of successfully versus unsuccessfully completed Match Problems revealed activation in right ventral lateral PFC (BA 47), left middle frontal gyrus (BA 9) and left frontal pole (BA 10), thus identifying the former as a critical component of the neural mechanisms of set-shift transformation. By contrast, activation in right dorsal lateral PFC (BA 46) covaried as a function of the number of solutions generated in Match Problems, possibly due to increased working memory demands to maintain multiple solutions 'on-line', conflict resolution, or progress monitoring. These results go beyond the patient data by identifying the ventral lateral (BA 47) aspect of right PFC as being a critical component of the neural systems underlying lateral transformations, and demonstrate a dissociation between right VLPFC and DLPFC in hypotheses generation and maintenance.

Adult↗

PubMed2004

Neuroanatomical correlates of aesthetic preference for paintings.

A study was conducted to determine the neuroanatomical correlates of aesthetic preference for paintings using fMRI. Subjects were shown representational and abstract paintings in different formats (original, altered, filtered), and instructed to rate them on aesthetic preference. Our primary results demonstrated that activation in right caudate nucleus decreased in response to decreasing preference, and that activation in bilateral occipital gyri, left cingulate sulcus, and bilateral fusiform gyri increased in response to increasing preference. We conclude that the differential patterns of activation observed in the aforementioned structures in response to aesthetic preference are specific examples of their roles in evaluating reward-based stimuli that vary in emotional valence.

Adult↗

PubMed2003

Creativity and inductive reasoning: the relationship between divergent thinking and performance on Wasons 246 task.

This study was an investigation of the relationship between potential creativityas measured by fluency scores on the Alternate Uses Testand performance on Wasons 246 task. As hypothesized, participants who were successful in discovering the rule had significantly higher fluency scores. Successful participants also generated higher frequencies of confirmatory and disconfirmatory hypotheses, but a multiple regression analysis using the stepwise method revealed that the frequency of generating disconfirmatory hypotheses and fluency scores were the only two significant factors in task outcome. The results also supported earlier studies where disconfirmation was shown to play a more important role in the later stages of hypothesis testing. This was especially true of successful participants, who employed a higher frequency of disconfirmatory hypotheses after receiving feedback on the first announcement. These results imply that successful participants benefited from the provision of feedback on the first announcement by switching to a more successful strategy in the hypothesis-testing sequence.

Adult↗