PubMed Health⌕ Search

Biomedical subjects

F H Duffy

Publications and source records attributed to F H Duffy.

9 recordsLinked to original sources
PubMed1979

Neuronal supersensitivity to acetylcholine induced by kindling in the rat hippocampus.

Kindling is an experimental model of epilepsy in which periodic brain stimulation induces the progressive development of electrical and behavioral seizures. A kindling-induced electrical seizure (afterdischarge) in the rat hippocampus produces prolonged neuronal supersensitivity to microiontophoretically applied acetylcholine after a latency of 40 to 60 minutes. Neuronal acetylcholine supersensitivity is correlated with the further progression of kindling. A larger hippocampal after-discharge is elicited by a subsequent kindling stimulus delivered in the presence of acetylcholine supersensitivity, but not by one delivered before the onset of the supersensitivity. The results suggest that alteration of synaptic sensitivity to acetylcholine may contribute to kindling and epileptogenesis.

Acetylcholine↗
PubMed1979

Brain electrical activity mapping (BEAM): a method for extending the clinical utility of EEG and evoked potential data.

The difficulties inherent in extracting clinically useful information by visual inspection alone from the massive amounts of data contained in multichannel polygraphic recordings have placed limits on the accuracy and range of utility of electroencephalography and evoked potentials. A method for condensing and summarizing the spatiotemporal information contained in recordings from multiple scalp electrodes is described. Data dimensionality is reduced and visibility increased by computer-controlled topographic mapping and display of data as color television images. Examples are given in which such brain electrical activity mapping (BEAM) (1) localizes tumors in patients with normal or nondiagnostic EEGs, (2) adds additional information to that visible on computerized axial tomography, and (3) demonstrates electrophysiological abnormalities in patients with functional lesions but normal CT scans. A sensitivity to the functional component of a neurological lesion suggests that BEAM may provide complementary information to the anatomical definition provided by the CT scan.

Adolescent↗
PubMed1978

Paroxysmal beta activity in the pediatric electroencephalogram.

A total of 5,401 electroencephalograms performed in the Seizure Unit at Children's Hospital Medical Center over a 12-month period were analyzed for the presence of paroxysmal beta activity. Nine examples were found in patients under the age of 10 years, each of whom had a clinical seizure disorder. Seven patients showed abnormalities such as tumor, cerebral dysgenesis, or hydrocephalus on CAT scans or skull roentgenograms. Paroxysmal beta activity should be considered a manifestation of a seizure disorder. Furthermore, the finding of paroxysmal beta activity on an electroencephalogram in the young child should lead to further evaluation for a possible structural lesion.

Beta Rhythm↗
PubMed1978

The pharmacology of amblyopia.

Physiologic and anatomic evidence has suggested an anatomic disconnection between the deprived eye and visual cortical neurons in cats made amblyopic by monocular deprivation. Clinical and visual-evoked response data suggest, however, that inhibition may play a major role in amblyopia. Accordingly, we intravenously administered anti-inhibitory compounds (bicuculline, ammonium ion, naloxone) to amblyopic cats and demonstrated a substantial restoration of binocular input to the visual cortex. Such pharmacologic reversal suggests that amblyopia is not an anatomically fixed lesion.

Adult↗
PubMed1975

Eye movement-related inhibition of primate visual neurons.

The influence of saccadic eye movements (EM) upon spontaneous neuronal activity was studied in the lateral geniculate nucleus (LGN) and striate visual cortex (VC) of encéphale isolé monkeys. EM were spontaneous and occurred in total darkness to eliminate the effects of retinal image displacement. The activity of LGN cells was not altered in association with EM. In contrast, 76% of cells studied in VC displayed a period of inhibition related to spontaneous EM in total darkness. EM-related inhibition of VC neurons was directionally specific; for each cell there was one quadrant of EM direction for which inhibition was most prominent. The majority of VC neurons showed inhibition in relation to EM directed into only one quadrant of the visual field. Reliable detection of EM-related inhibition required the formation of average histograms of neuronal firing time-locked to EM. For individual EM (even of optimum direction), a consistent degree of inhibition was not seen. The time course of EM-related inhibition of VC neurons is consistent with that reported for saccadic suppression. These results support the concept of a central mechanism (corollary discharge) acting at the cortical level being of significance in saccadic suppression.

Action Potentials↗