Biomedical subjects

S Kremen

Publications and source records attributed to S Kremen.

3 recordsLinked to original sources

PubMed2000

Neural substrates of orthographic lexical access as demonstrated by functional brain imaging.

OBJECTIVE: To delineate regions involved in visual word recognition. BACKGROUND: The processes and regions involved in visual word recognition have been somewhat controversial for over 100 years. METHODS: This study used regional cerebral blood flow as assessed by functional magnetic resonance imaging to study normal subjects (N = 9) on an individual within-subject basis while they were actively engaged on-line in a visual lexical decision task. Standard analysis techniques were used for identifying regions of activation. RESULTS: Across subjects, the task activated a number of regions, including the occipital pole, lateral and basal occipitotemporal (including lingual and fusiform) regions, superior and middle temporal gyri, and supramarginal and angular gyri. Typically, these regions were activated bilaterally; when activation was unilateral, it was on the left. Some of the areas activated (e.g., inferior parietal regions) have not been previously reported to be involved in such types of processing by activation studies but have been implicated in lesion studies. CONCLUSIONS: These results broaden the areas known to be involved in visual word recognition. The bilateral activation associated with visual word recognition is in some respects analogous to the "what" system in visual recognition described in subhuman primates. In addition, the study raises several methodologic issues. The within-subject analysis showed variability in the specific regions activated when subsequently comparing across individuals, raising implications for future functional imaging studies.

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PubMed1999

Neural pathways in tactile object recognition.

OBJECTIVE: To define further the brain regions involved in tactile object recognition using functional MRI (fMRI) techniques. BACKGROUND: The neural substrates involved in tactile object recognition (TOR) have not been elucidated. Studies of nonhuman primates and humans suggest that basic motor and somatosensory mechanisms are involved at a peripheral level; however, the mechanisms of higher order object recognition have not been determined. METHODS: The authors investigated 11 normal volunteers utilizing fMRI techniques in an attempt to determine the neural pathways involved in TOR. Each individual performed a behavioral paradigm with the activated condition involving identification of objects by touch, with identification of rough/smooth as the control. RESULTS: Data suggest that in a majority of individuals, TOR involves the calcarine and extrastriatal cortex, inferior parietal lobule, inferior frontal gyrus, and superior frontal gyrus-polar region. CONCLUSIONS: TOR may utilize visual systems to access an internal object representation. The parietal cortices and inferior frontal regions may be involved in a concomitant lexical strategy of naming the object being examined. Frontal polar activation likely serves a role in visuospatial working memory or in recognizing unusual representations of objects. Overall, these findings suggest that TOR could involve a network of cortical regions subserving somatosensory, motor, visual, and, at times, lexical processing. The primary finding suggests that in this normal study population, the visual cortices may be involved in the topographic spatial processing of TOR.

Adult↗

PubMed1998

Mapping attractor fields in face space: the atypicality bias in face recognition.

A familiar face can be recognized across many changes in the stimulus input. In this research, the many-to-one mapping of face stimuli to a single face memory is referred to as a face memory's 'attractor field'. According to the attractor field approach, a face memory will be activated by any stimuli falling within the boundaries of its attractor field. It was predicted that by virtue of its location in a multi-dimensional face space, the attractor field of an atypical face will be larger than the attractor field of a typical face. To test this prediction, subjects make likeness judgments to morphed faces that contained a 50/50 contribution from an atypical and a typical parent face. The main result of four experiments was that the morph face was judged to bear a stronger resemblance to the atypical face parent than the typical face parent. The computational basis of the atypicality bias was demonstrated in a neural network simulation where morph inputs of atypical and typical representations elicited stronger activation of atypical output units than of typical output units. Together, the behavioral and simulation evidence supports the view that the attractor fields of atypical faces span over a broader region of face space that the attractor fields of typical faces.

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