Biomedical subjects

C E Tenke

Publications and source records attributed to C E Tenke.

28 records · Page 2Linked to original sources

PubMed1992

Abnormal cerebral laterality in bipolar depression: convergence of behavioral and brain event-related potential findings.

Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field and dichotic listening measures of perceptual asymmetry. The results replicate our prior finding of abnormal laterality in bipolar depressed patients on a visuospatial test. Bipolar patients (n = 11) failed to show the left visual field (right hemisphere) advantage for dot enumeration seen for both unipolar patients (n = 43) and normal controls (n = 24). Bipolar patients performed significantly poorer than unipolar patients on normal controls for left visual field, but not right visual field stimuli. An electrophysiological correlate of abnormal visual field asymmetry in bipolar depression was found in brain event-related potentials recorded during audiospatial and temporal discrimination tasks. Bipolar patients had smaller N100 amplitudes for test stimuli in the left than right hemifield, whereas unipolar patients and normals did not. The origins of left hemifield deficits in bipolar depression are discussed in terms of right-sided dysfunction of an arousal/attentional system involving temporoparietal and possibly frontal regions.

Adolescent↗

PubMed1991

Striate cortical contribution to the surface-recorded pattern-reversal VEP in the alert monkey.

The striate cortical contribution to the surface pattern-reversal visual evoked potential (VEP) was investigated in awake monkeys during performance of a visual fixation task, by examining laminar profiles of VEP, current source density (CSD) and concomitant multiunit activity (MUA) in Area 17, recorded simultaneously at incremental depths using multicontact electrodes. Stimuli were black/white bar gratings centered on the fixation point. The typical surface pattern-reversal VEP over striate cortex consists of a prominent positivity peaking at 50-70 msec (P60), followed by a large negativity peaking at approx. 80 msec (N80), and then by a late broad positivity, peaking between 120 and 150 msec (P125). P60 is often preceded by a small negativity peaking at 45-55 msec (N50), and on rare occasions a small positivity (P40) is also observed. N50 is generated primarily by current sinks in Lamina 4C. P60 arises from large current sources in the supragranular laminae. N80 and P125 appear to be composite waveforms reflecting complex contributions from local activity and from activity occurring outside of the foveal/immediate parafoveal representation in Area 17. The basic physiologic sequence elicited by patterned stimulation is similar to that elicited by diffuse luminance or by electrical stimulation, but is characterized by more prominent supra- and infragranular activation. It is consistent with the cellular and synaptic anatomy of Area 17: initial activation of the thalamorecipient subdivisions of Lamina 4C, followed by activation of mid/upper Lamina 4 and of supra- and infragranular laminae. Our results suggest the possibility of differentiating synaptic stages and cellular processes reflected in the human VEP, based on homologies with simian VEP components.

Animals↗

PubMed1991

The incidence of depressive symptomatology in juvenile sex offenders with a history of abuse.

Depressive symptomatology was assessed in a sample of 246 male juvenile sex offenders using the Beck Depression Inventory. Of these participants, the racial composition was black = 147, Hispanic = 62, Caucasian = 34. Three adolescents elected not to identify their racial origin. Subjects were divided according to their self-reports of having been sexually or physically abused. The mean Beck score across all subjects was 14.3, a value markedly higher than published norms and indicative of mild depression. Forty-two percent of subjects attained scores indicative of appreciable depressive symptomatology. A history of sexual or physical abuse was significantly related to high Beck scores; abused subjects had a mean Beck score of 16.4, as contrasted to 12.3 for nonabused subjects (Wilcoxon test: z = 2.82; p less than .005). This relationship was apparent across all racial groups. While Hispanic subjects tended to have higher Beck scores and Caucasians lower scores, racial differences were not statistically significant. Results indicate that juveniles who have committed sexual crimes, particularly those with a history of abuse, should be evaluated for depression.

Adolescent↗

PubMed1990

Binocularity in the lateral geniculate nucleus of the alert macaque.

We examined the timing and the laminar distribution of binocular interactions and non-dominant eye effects in the lateral geniculate nucleus (LGN) of the alert macaque. Flash-evoked multiunit activity (MUA) was recorded simultaneously from multiple LGN laminae during contralateral eye, ipsilateral eye and binocular stimulation. Evidence of binocularity was noted in all laminae except 4. Inhibitory effects included (1) binocular suppression, a 15-70% reduction in the peak amplitude of MUA during binocular, compared to monocular stimulation of the dominant eye for that lamina, and (2) non-dominant suppression, a 10-45% reduction in MUA below its spontaneous level, with stimulation of the non-dominant eye. In lamina 3, the onset of this effect often preceded that of the excitatory response to stimulation of the dominant eye, and was coincident with non-dominant suppression in lamina 2, and with the dominant eye-mediated excitatory response in contralaterally innervated lamina 1. This is consistent with a parvo/magnocellular interaction. Corresponding excitatory effects, binocular and non-dominant facilitation, were also noted throughout LGN. The latter occurred both within the time frame of retinally driven activity (15-65 ms), and at longer latencies as well. The earliest response in lamina 6 of striate cortex, the origin of the corticogeniculate projections, was 30-35 ms, thus precluding a role of corticofugal modulation in the earlier effects in LGN.

Action Potentials↗

PubMed1990

Laminar analysis of bicuculline-induced epileptiform activity in area 17 of the awake macaque.

We investigated the laminar profile of visually evoked paroxysmal discharge following bicuculline administration in area 17 of the alert macaque. Paroxysmal discharge was focussed in lamina 3, with lesser concomitants in infragranular laminae. There were no marked effects on the flash-evoked laminar activation sequence. The neocortex of the alert macaque studied with the present techniques may provide a model for evaluating basic mechanisms of epilepsy, and for linking these to the macroscopic phenomena seen in humans.

Animals↗

PubMed1989

Timing and distribution of flash-evoked activity in the lateral geniculate nucleus of the alert monkey.

Simultaneous recording of activity from multiple cortical laminae in alert monkeys, using multichannel electrodes, has been used to identify the intracranial generators of surface-recorded, visually evoked potentials (VEP) to stroboscopic flash. Beyond their clinical implications, these results offer an unique view of the timing and sequence of cortical visual processing in the alert monkey, including the somewhat surprising findings of an extremely short-latency response in lamina IVA, a contra- over ipsilateral latency advantage throughout lamina IV, and the lack of a consistent flash-evoked response in the major cortical recipient of the magnocellular system, lamina IVCa. The present study used similar techniques to examine flash-evoked activity in LGN and in optic tract, both to elucidate the role of the subcortical pathways in establishing this pattern, and to provide a parallel, detailed view of the timing of visual activity in LGN and optic tract in the alert monkey. Flash-evoked responses are robust in both parvo- and magnocellular laminae, but these responses differ along several dimensions: (1) parvocellular multiunit activity (MUA) is 1/4 to 1/2 the amplitude of magnocellular MUA; (2) oscillatory activity is higher in frequency and shorter in duration in parvo- than in magnocellular responses; (3) inhibitory processes appear less prominent and diverse in parvo- than in magnocellular activity; (4) mean onset latencies of MUA are longer in parvo- than in magnocellular laminae, but there is extensive overlap in these distributions. Latencies encountered in ipsilateral lamina 3, and at laminar borders dorsal to 3, group more clearly with those of the magnocellular laminae than with those of the other parvocellular laminae. As a result, in the parvocellular division as a whole, the average latency to ipsilateral stimulation is shorter than that to contralateral stimulation. The optic tract exhibits a dorsal-to-ventral progression of onset latency and oscillation frequency consistent with a dorsal/ventral segregation of the inputs to parvo- and magnocellular layers. Comparison of optic tract and LGN data reveals that while many LGN response characteristics are initiated in the retina, significant modification of retinal output occurs at LGN. The techniques used here permit a particularly sensitive and reliable assessment of the timing and distribution of visual responses in the optic tract and LGN of alert monkeys. Our data support the view that in the alert monkey, the surface-VEP to passive, binocular flash primarily reflects activation of parvocellular thalamorecipient laminae of Area 17.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1987

Movement-related potentials within the hippocampal formation of the monkey.

A series of large amplitude potentials were recorded within and surrounding the hippocampal formation in association with repetitive, self-paced hand movements in the monkey. The earliest component precedes the onset of muscle contraction by approximately 100 ms, inverts in polarity across the pyramidal cell layer of CA3 and CA1 and is coincident with increased local multiple unit activity (MUA). Later components, generated within the hippocampal formation, follow the muscle contraction by as much as 600 ms and are not associated with net changes in MUA. The onset of voluntary movements is often associated with desynchronization of low-frequency rhythmic hippocampal EEG patterns and these changes antecede the movement. The findings strongly suggest that the hippocampal formation is involved in the initiation and control of even simple voluntary movements in the primate.

Animals↗

PubMed1986

Statistical characterization of the EEG: the use of the power spectrum as a measure of ergodicity.

In order to interpret statistical summaries of treatment-related changes in EEG power spectra, the internal consistency of the set of data from each condition must first be known. A technique for the assessment of such across-record homogeneity (ergodicity) is derived from the defining characteristics of the power spectrum. A simplified graphic approximation is also detailed. Computer simulations and practical validation confirm it as a useful means of evaluating the ergodicity of sets of EEG data.

Electroencephalography↗

PubMedDate not supplied

Subcortical contributions to the surface-recorded flash-VEP in the awake macaque.

Epidural mapping of flash-VEP in awake monkeys revealed a reliable, short latency negativity, N25 (onset: 18-22 msec; peak: 23-27 msec; duration: 15-20 msec), with a broad frontal surface distribution (frontolateral maximum). N25 was dissociable from the electroretinogram (ERG), from cortical VEP and from the high frequency oscillations (wavelets) coextensive with the ERG and with cortical VEP. Depth recordings traced N25 from its surface maximum down to the lateral geniculate nucleus (LGN). Concomitant VEP, current source density (CSD) and multiunit activity (MUA) profiles obtained with multicontact electrodes showed that the peak and later portion of N25 arise primarily from current sinks (associated with MUA increases) that reflect transmembrane current flow attending depolarization of cells in lamina 6, the uppermost lamina, but may also receive contributions from the more ventral LGN laminae. The initial portion of N25 arises from similar processes near the lamina 3/2 border. Wavelets, in contrast, are prominent in VEP, CSD and MUA within LGN, but attenuate rapidly above LGN. LGN laminar and cellular morphology predict volume conduction of N25 over a wide arc lateral and anterior to LGN and roughly horizontal isopotential planes medial and posterior to LGN. Recordings on the brain surface, within LGN, and in the regions surrounding LGN are consistent with these predictions. Possible contributions from other structures and how these results fit with data obtained in humans are considered.

Animals↗

PubMedDate not supplied

Cellular generators of the cortical auditory evoked potential initial component.

Cellular generators of the initial cortical auditory evoked potential (AEP) component were determined by analyzing laminar profiles of click-evoked AEPs, current source density, and multiple unit activity (MUA) in primary auditory cortex of awake monkeys. The initial AEP component is a surface-negative wave, N8, that peaks at 8-9 msec and inverts in polarity below lamina 4. N8 is generated by a lamina 4 current sink and a deeper current source. Simultaneous MUA is present from lower lamina 3 to the subjacent white matter. Findings indicate that thalamocortical afferents are a generator of N8 and support a role for lamina 4 stellate cells. Relationships to the human AEP are discussed.

Acoustic Stimulation↗