Biomedical subjects

S D Newman

Publications and source records attributed to S D Newman.

3 recordsLinked to original sources

PubMed2001

Differences in auditory processing of words and pseudowords: an fMRI study.

Although there has been great interest in the neuroanatomical basis of reading, little attention has been focused on auditory language processing. The purpose of this study was to examine the differential neuroanatomical response to the auditory processing of real words and pseudowords. Eight healthy right-handed participants performed two phoneme monitoring tasks (one with real word stimuli and one with pseudowords) during a functional magnetic resonance imaging (fMRI) scan with a 4.1 T system. Both tasks activated the inferior frontal gyrus (IFG), the posterior superior temporal gyrus (pSTG) and the inferior parietal lobe (IPL). Pseudoword processing elicited significantly more activation within the posterior cortical regions compared with real word processing. Previous reading studies have suggested that this increase is due to an increased demand on the lexical access system. The left inferior frontal gyrus, on the other hand, did not reveal a significant difference in the amount of activation as a function of stimulus type. The lack of a differential response in IFG for auditory processing supports its hypothesized involvement in grapheme to phoneme conversion processes. These results are consistent with those from previous neuroimaging reading studies and emphasize the utility of examining both input modalities (e.g., visual or auditory) to compose a more complete picture of the language network.

Acoustic Stimulation↗

PubMed2001

Baseline conditions and subtractive logic in neuroimaging.

Discrepancies in the patterns of cortical activation across studies may be attributable, in part, to differences in baseline tasks, and hence, reflect the limits of the subtractive logic underlying much of neuroimaging. To assess the extent of these effects, three of the most commonly used baseline conditions (rest, tone monitoring, and passive listening) were compared using phoneme discrimination as the experimental task. Eight participants were studied in a fMRI study with a 4.1 T system. The three baseline conditions systematically affected the amount of activation observed in the identical phoneme task with major affects in Broca's area, the left posterior superior temporal gyrus, and the left and right inferior parietal regions. Two central findings were: 1) a differential effect of baseline within each region, with the rest baseline condition producing the greatest amount of activation and the passive listening condition producing the least, and 2) systematic baseline task activation in the inferior parietal regions. These results emphasize the relativity of activation patterns observed in functional neuroimaging, and the necessity to specify the baseline processes in context to the experimental task processes.

Adult↗

PubMed1992

Tolerance to spherical aberration induced by rigid contact lenses.

We have investigated the effects of spherical aberration (SA) on visual performance by fitting subjects with rigid lenses of varying front surface asphericity. Three pairs of lenses were worn by each subject with front surface asphericities of Q = 0 (conventional spherical surface), Q = -0.26 (similar to the average corneal asphericity) and Q = -0.51. The calculated average change in spherical aberration induced by each pair of contact lenses in photopic conditions was +0.02 D (Q = 0), -0.49 D (Q = -0.26) and -0.94 D (Q = -0.51). In mesopic conditions these same lenses induced an average change in spherical aberration of +0.01 D (Q = 0), -1.18 D (Q = -0.26) and -2.16 D (Q = -0.51). In this double-blind study, 12 adapted, low to moderate myopic rigid lens wearers wore each pair of lenses for one week and noted visual performance. With each pair of lenses we also measured the subject's visual acuity with high and low contrast logMAR charts. All measurements were conducted using the right eye at distance in photopic and mesopic conditions. When forced to select the lenses they would accept as compensation for participation in the study, most subjects (9 out of 12) chose the Q = 0 lenses, 3 subjects those the Q = -0.26 lenses and none of the subjects chose the Q = -0.51 lenses. Visual performance measures showed little difference between the Q = 0 and Q = -0.26 lenses. However, the Q = -0.51 lenses significantly reduced visual acuity in mesopic conditions with the low contrast acuity chart.

Contact Lenses↗