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Biomedical subjects

M W Torello

Publications and source records attributed to M W Torello.

17 recordsLinked to original sources
PubMed2001

Elevated motor threshold in drug-free, cocaine-dependent patients assessed with transcranial magnetic stimulation.

BACKGROUND: Transcranial magnetic stimulation (TMS) provides a noninvasive method of examining cortical inhibitory and excitatory processes and cortical excitability in awake subjects. There is evidence from clinical and electroencephalographic (EEG) data that cortical excitability may be abnormal in some psychiatric populations. Chronic cocaine abuse influences a number of neurotransmitters that are involved in the excitatory/inhibitory balance of the cerebral cortex. This pilot study was conducted to ascertain the possible utility of TMS in examining cortical excitability in a population of chronic cocaine abusers. METHODS: The right and left motor thresholds of ten cocaine-dependent subjects, according to DSM-IV, and ten normal control subjects were examined using single pulse TMS. RESULTS: The resting motor thresholds resulting from stimulation of the right or the left motor cortical regions were significantly elevated in cocaine-dependent subjects compared with matched control subjects. CONCLUSIONS: These pilot data suggest that chronic cocaine use significantly alters cortical excitability in the direction of increased inhibition or decreased excitability. We hypothesize that this observation reflects adaptation to those effects of cocaine intoxication that promote cortical excitability and seizures.

Adult↗
PubMed1997

Auditory event-related potentials and statistical probability mapping in obsessive-compulsive disorder.

The current exploratory investigation was undertaken to replicate and extend previous findings of auditory event related potentials (ERPs) observed in obsessive-compulsive disorder (OCD). Similar to previous ERP studies, this study revealed a decreased slow wave (SW) (post P300) latency, a trend towards decreased P300 latency and a greater N200 amplitude in OCD subjects than in controls. In addition, the chronicity of OCD symptoms was correlated with the 140-170 millisecond integrated amplitude and the severity of OCD symptoms correlated with the 386-438 millisecond integrated amplitude. Current findings lend additional support to evidence suggesting OCD represents, in part, hyperarousal of the cortex.

Adult↗
PubMed1995

Evoked potentials in subjects at risk for Alzheimer's disease.

Evoked potential (EP) changes accompanying dementing processes have been documented in a number of studies. However, EPs have not been studied in subjects who are at heightened risk for the development of Alzheimer's Disease (AD). Nineteen volunteers with no immediate family members with a history of AD and 33 healthy subjects with at least one first-degree relative with AD were studied. Of the 33 subjects with a positive family history of AD, the illness of the sick relative was classified as possible AD in 10 subjects, probable AD in 17 subjects, and definite (autopsy-proven) AD in 6 subjects. Mid-latency evoked potentials (P50, N100, and P200) and P300 event-related potentials were recorded in an oddball paradigm. The amplitudes of the P50 responses to the frequent stimuli and of the P300 responses were significantly higher in the subjects whose relatives had definite AD as compared with the other three groups. The amplitude of the N100 component was also larger in the same group, but the difference was only statistically significant from the group of healthy volunteers without a family history of AD. A process of increased sensitivity to incoming stimuli may be reflected in the increased P50, N100, and P300 amplitudes in the subjects at increased risk for developing AD.

Alzheimer Disease↗
PubMed1995

The P50 evoked potential component and mismatch detection in normal volunteers: implications for the study of sensory gating.

Sensory gating is a complex, multistage, multifaceted physiological function believed to be protecting higher cortical centers from being flooded with incoming irrelevant sensory stimuli. Failure of such mechanisms is hypothesized as one of the mechanisms underlying the development of psychotic states. Attenuation of the amplitude of the P50 evoked potential component with stimulus repetition is widely used to study sensory gating. In the current study, we investigated the responsiveness of the P50 component to changes in the physical characteristics of ongoing trains of auditory stimuli. Forty normal volunteers were studied in a modified oddball paradigm. At all cerebral locations studied, P50 amplitudes were higher in response to infrequent stimuli. We postulate that the increase in P50 amplitude reflects the system's recognition of novel stimuli or "gating in" of sensory input. The ratio of the amplitude of the responses to the infrequent stimuli to those of the frequent stimuli was significantly higher for the posterior temporal regions. This finding provides further evidence that the temporal lobes may be significantly involved in sensory gating processes. Although this study only included normal subjects, the data generated contribute to the understanding of sensory gating mechanisms that may be relevant to psychotic states.

Adolescent↗
PubMed1993

Vocal perception: brain event-related potentials in a chimpanzee.

We describe the first brain event-related potential (ERP) study of cognitive processes in the chimpanzee. In an extension of our studies on the ontogeny of vocal perception, ERP measures were obtained during the presentation of simple nonsignal stimuli as well as conspecific and human vocalizations. We initially confirmed findings from humans and monkeys of the appearance of a long-latency positivity in the ERP waveform to a rare stimulus in an oddball paradigm. This ERP component is reminiscent of the P3a reported in humans under similar (passive) experimental conditions. We further demonstrated that both conspecific and human vocal stimuli having affective significance also enhanced late positive components of the ERP. These late positive components displayed a predominant fronto-central distribution, with a maxima at Cz. Additionally, responses to adaptively significant vocal stimuli showed a right hemisphere laterality, whereas no significant laterality was observed with the rare stimulus in the oddball paradigm. Results document the feasibility of ERP measures in chimpanzees and their potential utility in the study of the ontogeny and phylogeny of vocal perception.

Animals↗
PubMed1990

Leukoaraiosis in asymptomatic adult offspring of individuals with Alzheimer's disease.

The presence of white matter changes on magnetic resonance imaging (MRI), which has been referred to by Hachinski (1987) as leukoaraiosis, is frequently noted in elderly individuals in conditions ranging from health to frank dementia. This study involved the use of MRI to document cerebral structure if 41 healthy 50-60-year-old individuals, 28 of whom were offspring of Alzheimer's disease victims. On visual inspection of spin-echo images, 13 of the 28 offspring showed white matter lesions whereas all of the controls were free of leukoaraiosis. This statistically significant difference suggests that the presence of leukoaraiosis might be of importance in understanding changes in the white matter among populations at increased risk for Alzheimer's disease.

Alzheimer Disease↗
PubMed1989

Topographic mapping of EEG and evoked potentials in psychiatry: delusions, illusions, and realities.

This paper reviews the utility of topographic mapping of EEG and evoked potentials in psychiatry. Further, a wide variety of caveats related to this technique are reviewed including cerebral and extracerebral sources of artifact. Moreover, both questionable and legitimate uses of mapping in psychiatry are addressed and possible future applications of this technique are considered. Finally, multidisciplinary approaches to the study of the brain are discussed.

Brain Mapping↗
PubMed1989

Event-related brain potentials in depressed patients treated with electroconvulsive therapy.

1. As impairment of attention has long been recognized as a clinical feature of depression, we undertook to evaluate in depressed subjects and controls a feature of the event-related brain potentials (ERP) the N100 wave which has been linked to attentional processes. 2. This study involved collection of EEG data in an "auditory oddball" ERP paradigm in 9 depressed subjects prior to and following a course of 6 electroconvulsive therapy (ECT) treatments, as well as 11 controls. Concurrent Hamilton depression rating scales provided a measure of symptomatic severity. 3. Pretreatment N100 amplitude was significantly lower in the depressed group while N100 latency was greater than among controls, with treatment differences from control values disappeared. Further a robust correlation (r = 0.85 p less than or equal to .0038) emerged between N100 amplitude (increased amplitude being lower) and severity of depression. 4. Those results provide evidence for a physiological attentional disturbance in depression and suggest that certain features of this disturbance relate directly to symptom severity.

Adult↗
PubMed1988

P300 in schizophrenia: confirmation and statistical validation of temporal region deficit in P300 topography.

Comparison of normal and medicated schizophrenic groups on the auditory P300 component of the event-related potential confirmed our earlier finding of a left temporal deficit in P300 amplitude in schizophrenia. A difference in P300 topography between groups was evident in both color mapping and in grand-averaged waveforms, which was statistically validated by the presence of a group-by-scalp region interaction (p less than 0.05). The left temporal area in schizophrenics was denoted as the region of greatest deficit and of maximal statistical separation (p less than 0.05) relative to normals by t statistic mapping (SPM), Hotelling's T-squared "protected" contrasts of individual scalp regions, and the relative ratio of left scalp amplitudes to right scalp amplitudes. The left temporal scalp region yielding maximal group separation in the previous study also statistically separated the schizophrenic group from the normal group. This feature correctly differentiated 9 of 11 schizophrenics and 7 of 9 controls. These findings are compatible with other histological, metabolic, and electrophysiological studies suggesting temporal lobe abnormality in schizophrenia.

Adult↗
PubMed1988

Differentiation of schizophrenics and normal controls is enhanced by the Goodin subtraction procedure.

The P300 event-related potential as calculated by the Goodin subtraction procedure (P300g) combines attentive and inattentive condition waveforms in order to isolate components specifically related to target stimulus processing. The waveform was compared with the more commonly employed unsubtracted P300 waveform associated with attended infrequent stimuli (P300ia). The P300g produced the largest overall schizophrenic and control group differences in mean integrated amplitude compared with the P300ia. A group by scalp region interaction in the P300g, indicative of group topographic alterations, was also noted which was not present in the unsubtracted P300ia. Furthermore, the P300g pinpointed the single best scalp region (left temporal) for maximal group separation. This temporal asymmetry was found to originate in the inattentive condition waveforms, indicating a possible abnormality in "nonvoluntary" processing. We conclude that combining attentive and inattentive condition waveforms to form the P300g enhanced clinically relevant group differences between schizophrenics and normals compared with the P300ia.

Acoustic Stimulation↗
PubMed1983

An automated method for measurement of circling behavior in the mouse.

Circling behavior in animals lesioned unilaterally in one striatum with 6-hydroxydopamine is widely used to test pharmacological compounds with dopaminergic activity. Although automated techniques employed to record this behavior have previously been reported, most of these methods either limit the movement of the animal or are less reliable for various reasons. This paper describes a new method which allows the free movement of the animal in addition to recording the circling behavior automatically. Furthermore, this device provides new and unique data on the diameter and total area of the circles that are circumscribed by the animal. Consequently, the present device may prove to be a better and more reliable tool to assess the pharmacological effect of drugs on the striatal dopaminergic system.

Amphetamine↗
PubMed1983

Vasopressin-induced antinociception: an investigation into its physiological and hormonal basis.

Systemically administered lysine-8-vasopressin (LVP; 16-128 micrograms/kg) was found to induce a potent and dose-dependent antinociceptive effect, as measured by the tail-flick test in the rat. This effect could be seen in the absence of any significant change in general activity, indicating that it was not due to sedation or general motor debilitation. The antinociceptive effect of LVP does not appear to be mediated by endogenous opiates or other pituitary hormones, as evidenced by: 1) the lack of antagonism by the opiate receptor blocker naloxone, 2) the lack of cross-tolerance with morphine, and 3) its persistence after hypophysectomy. Des-glycinamide-LVP, a vasopressin analog with no appreciable pressor or antidiuretic action, showed no antinociceptive activity (128 micrograms/kg), and des-amino-arginine-vasopressin, a vasopressin analog with minimal pressor activity but greatly enhanced antidiuretic activity, was also relatively ineffective (128 micrograms/kg). These results suggest that the antinociceptive activity of vasopressin may be related to receptor types similar to those mediating its pressor effects. Nevertheless, the antinociceptive action of vasopressin does not appear to be secondary to its pressor activity, since phenylephrine failed to induce an antinociceptive effect at a dosage that mimicked the pressor response to vasopressin. These results are in concert with a growing body of evidence suggesting that vasopressin may be one of several nonopiate peptides that play a role in the modulation of pain sensitivity.

Animals↗
PubMedDate not supplied

An atlas of the deep cerebellar nuclei and subtentorial brainstem of the cat with compensation for skull-size.

The bony tentorium in the cat precludes a stereotaxic approach, in the coronal plane, to widespread areas of the cerebellum and underlying brainstem. To facilitate the application of the stereotaxic method in these areas, an atlas of the subtentorial brainstem was prepared, with plates (30 degrees from the vertical) based on an angle of entry which avoids the tentorium. In addition, a placement error regression function, based on a measure of skull size, was derived to provide atlas coordinate corrections for different brain sizes. The application of this regression function, together with the present atlas plates, can greatly increase placement accuracy.

Animals↗