mRNA stability and polysome loss in hibernating Arctic ground squirrels (Spermophilus parryii).

All small mammalian hibernators periodically rewarm from torpor to high, euthermic body temperatures for brief intervals throughout the hibernating season. The functional significance of these arousal episodes is unknown, but one suggestion is that rewarming may be related to replacement of gene products lost during torpor due to degradation of mRNA. To assess the stability of mRNA as a function of the hibernation state, we examined the poly(A) tail lengths of liver mRNA from arctic ground squirrels sacrificed during four hibernation states (early and late during a torpor bout and early and late following arousal from torpor) and from active ground squirrels sacrificed in the summer. Poly(A) tail lengths were not altered during torpor, suggesting either that mRNA is stabilized or that transcription continues during torpor. In mRNA isolated from torpid ground squirrels, we observed a pattern of 12 poly(A) residues at greater densities approximately every 27 nucleotides along the poly(A) tail, which is a pattern consistent with binding of poly(A)-binding protein. The intensity of this pattern was significantly reduced following arousal from torpor and undetectable in mRNA obtained from summer ground squirrels. Analyses of polysome profiles revealed a significant reduction in polyribosomes in torpid animals, indicating that translation is depressed during torpor.

Event-related potentials in cross-modal divided attention in autism.

The behavior and event-related potentials (ERPs) of high functioning subjects with autism (Autism group) were contrasted with the results of normal controls (Control group) during a focused visual attention, a focused auditory attention and a visual/auditory divided attention task. Detecting targets by the Autism group in the cross-modal divided attention condition was more difficult (longer RTs, lower % of correct detections) than attending to one modality. However, both the Autism and Control groups performed all tasks above chance level. The slow negative wave (SNW) was the only negative component which reflected Focused vs Divided task effect in Controls, being largest to stimuli in single channel-focused attention, intermediate when attention was divided between targets of two modalities and smallest to unattended stimuli. Task effects were more evident in the positive peaks for the Autism group. No significant divided attention task effect was noted for P3b, although it was larger for attended than ignored stimuli, of normal morphology and only slightly decreased in size in the Autism group as compared to the Control group. The failure of the Autism group to modulate the slow negative wave in response to Focused/Divided/Ignored conditions in a normal manner, the presence of relatively normal morphology despite the reduced amplitude of the P3b and other positive components, together with the high level of correct target detections are discussed in the context of a selective inhibition deficit and an alternative mechanism of selective attention in autism.

Somatosensory evoked magnetic fields in patients with stroke.

We used magnetoencephalography to evaluate areas of sensory cortex in patients with ischemic strokes involving the somatomotor system. We measured somatosensory evoked magnetic fields using a 7-channel neuromagnetometer and estimated the location of cortical responses to median nerve stimulation in 5 patients with cortical or subcortical strokes involving the somatomotor system. All patients underwent quantitative neurological examinations and a high resolution volumetric magnetic resonance imaging. The estimated current dipoles were localized onto the patient's own MRI scan in all patients with measurable responses. The location of the estimated dipole was always in non-infarcted tissue in the anatomical region of the somatosensory cortex. In 1 patient the somatosensory dipole localized to a peninsula of cortex flanked by infarcted tissue. Single photon emission computed tomography found the localized area of cortex to have significant blood flow. The estimated current dipole strengths of somatosensory evoked fields from median nerve stimulation correlated significantly (r = 0.95, P < 0.02) with the patient's ability to recognize numbers written on the involved palm (graphesthesia). The combination of evoked magnetic field recording and magnetic resonance imaging is a promising non-invasive technology for studying brain function in patients with cerebrovascular disease.

Cerebellar abnormality in autism: a nonspecific effect of early brain damage?

Cerebellum may be a common site of developmental abnormalities due to its protracted course of maturation. Recent studies have implicated morphological deviations of the cerebellum as responsible for specific behavioral and cognitive manifestations of autism. We investigated neuropsychology and quantitative MRI of the cerebellum in both high functioning subjects with autism and survivors of childhood leukemia treated with radiation and intrathecal chemotherapy. The results of neuropsychological testing revealed different patterns of cognitive deficits for the two groups, while the abnormal cerebellar morphology was similar for both groups. Since it is suggested that the cerebellum contributes to motor-attentional subsystems, the present data provide support for a cerebellar role in the governance of higher cognitive functions, found to be abnormal in both groups. However, the abnormal macromorphology of the cerebellar vermis described here appears to be non-specific to autism.

Cortical organization in adulthood is modified by neonatal infarct: a case study.

PURPOSE: To assess anomalous cortical organization of somatosensory function in a 23-year-old man who had had a neonatal infarct involving the left middle cerebral artery. MATERIALS AND METHODS: The infarct destroyed the primary and secondary somatosensory areas of the subject's left hemisphere but caused only mild perturbation of somatosensation on the right side of his body. With magnetic source imaging, the authors integrated magnetoencephalographic data with magnetic resonance imaging data to create magnetic source localization images that showed the mapping between brain function and structure. RESULTS: Electrical stimulation of the right median nerve evoked activity in two nontraditional areas: (a) an intact region of the left inferior temporal gyrus and (b) the ipsilateral right medial parietal cortex. CONCLUSION: These data suggest that bilateral neural reorganization can be induced by unilateral neonatal damage.

Overinclusion, broad scanning, and picture recognition in schizophrenics.

Difficulty of picture and word recognition was manipulated to test the hypothesis that schizophrenics have adequate recognition memories and to determine whether overinclusion is related to a good visual recognition memory. Good and poor premorbid, acute and chronic schizophrenics were compared to nonpsychotic psychiatric patients and to hospital aides. Both Payne's Object Classification Test and Goldstein-Scheerer's Object Sorting Test were given to all the patients, but only the former differentiated among the diagnostic subgroups and was related to good picture memory. When the measures of overinclusion, chronicity, premorbidity and intelligence were used as independent variables in a multiple regression, only Payne NonA predicted success on the picture task. Good premorbid schizophrenics recognized pictures as well as normals and nonpsychotics, but poor premorbids' picture memory was significantly worse. No experimental variable predicted word performance in a multiple regression, and good premorbids did not differ from poor premorbids on their word recognition. The authors favored the interpretation that the pattern of performance of overinclusive schizophrenics reflects their tendency to scan broadly both important and unimportant features of stimuli.