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E J Neafsey

Publications and source records attributed to E J Neafsey.

54 records · Page 3Linked to original sources
PubMed1986

A comparative topographical analysis of dorsal column nuclear and cerebral cortical projections to the basilar pontine gray in rats.

The somatotopic distribution of dorsal column nuclear projections within the basilar pontine gray was examined in relation to the massive corticopontine projection system that emanates most heavily from motor and somatosensory cortex. The distribution patterns of these two systems were compared by combining autoradiographic and degeneration axonal tracing methods within individual animals. Stereotaxic injections of tritiated leucine (50 microCi/microliter) and lesions by aspiration were made in animals under ketamine hydrochloride anesthesia. The forelimb cortical injections (0.1-0.3 microliter) were centered in either sensory or motor cortical regions as determined by intracortical microstimulation and multiunit recording techniques. Because sensory and motor hindlimb cortical areas overlap extensively in the rat, hindlimb cortical injections (0.1-0.3 microliter) were limited to a single hindlimb sensorimotor cortical region. The corresponding contralateral dorsal column nucleus, cuneatus or gracilis, was then aspirated. A somatotopic distribution of fore- and hindlimb corticopontine fibers were found in discrete regions of the ipsilateral pontine gray. Hindlimb sensorimotor corticopontine fibers distributed caudal to forelimb projections. Similarly, pontine afferents from the dorsal column nuclei terminated somatotopically in the caudal half of the contralateral pontine gray in that gracilopontine fibers distributed caudal to cuneopontine fibers. Within individual animals, partially overlapping terminations were seen from nucleus cuneatus and the forelimb sensory cortical area as well as from nucleus gracilis and the hindlimb sensorimotor cortical area. No overlap existed in the pontine terminations from nucleus cuneatus and the forelimb motor cortical area.

Animals↗
PubMed1986

The organization of the rat motor cortex: a microstimulation mapping study.

In conclusion, the rat primary motor cortex appears to be organized into irregularly shaped patches of cortex devoted to particular movements. The location of major subdivisions such as the forelimb or hindlimb areas is somatotopic and is consistent from animal to animal, but the internal organization of the pattern of movements represented within major subdivisions varies significantly between animals. The motor cortex includes both agranular primary motor cortex (AgL) and, in addition, a significant amount of the bordering granular somatic sensory cortex (Gr(SI)), as well as the rostral portion of the taste sensory insular or claustrocortex (Cl). The rat frontal cortex also contains a second, rostral motor representation of the forelimb, trunk and hindlimb, which is somatotopically organized and may be the rat's supplementary motor area. Both of these motor representations give rise to direct corticospinal projections, some of which may make monosynaptic connections with cervical enlargement motoneurons. Medial to the primary motor cortex, in cytoarchitectonic field AgM, is what appears to be part of the rat's frontal eye fields, a region which also includes the vibrissae motor representation. The somatic motor cortical output organization pattern in the rat is remarkably similar to that seen in the primate, whose primary, supplementary and frontal eye field cortical motor regions have been extensively studied.

Animals↗
PubMed1985

Electrophysiological analysis of motor cortical plasticity after cortical lesions in newborn rats.

Intracortical microstimulation of the motor cortex in normal adult rats evoked low threshold contralateral forelimb movements and high threshold ipsilateral movements. Ablation of the opposite sensorimotor cortex in adult animals did not alter these thresholds. However, stimulation of the unablated hemisphere in adult rats that sustained unilateral sensorimotor cortical lesions as neonates elicited low threshold ipsilateral forelimb movements that were similar to contralateral movements. These low threshold ipsilateral movements may be mediated via aberrant corticofugal pathways which are known to develop following neonatal cortical lesions.

Animals↗
PubMed1985

Beta-carboline analogues of N-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP): endogenous factors underlying idiopathic parkinsonism?

A remarkable structural similarity exists between the parkinsonian neurotoxin, N-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP), and 2-[N]-methyl-tetrahydro-beta-carboline (2M-THBC), a tryptamine-derived alkaloid which can be biosynthesized in brain. To explore whether the beta-carboline also has neurotoxic effects, owl monkeys were treated daily with MPTP or 2M-THBC. Acute behavioral similarities were seen, but 2M-THBC did not induce persistent parkinsonism, nor did it cause apparent loss of nigral cells. However, 2M-THBC resembled MPTP in reducing 3,4-dihydroxyphenylacetic acid levels in caudate and in altering levels of serotonin and 5-hydroxyindoleacetic acid in substantia nigra. These limited similarities should be considered in the light of relationships between neurotoxicity, MPTP versus 2M-THBC oxidation, and the chronicity of human Parkinson's disease. We suggest that N-methylated beta-carboline species, possibly accumulating during stress and aging, could well be causative factors in parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1984

Cytoarchitecture of the dorsal thalamus of the rat.

Although several neuroanatomical studies have previously described various subdivisions of the rat thalamus, no comprehensive description of the entire thalamus accompanied by photomicrographs has been available. To provide such a description, the cytoarchitecture of the normal rat thalamus was studied in the coronal plane using a series of celloidin embedded, Nissl-stained 33 micrometers sections spaced 400 micrometers apart. Using the criteria of cell packing density, relative cell size, and the presence or absence of fibers, the thalamus can be subdivided into a ventral nuclear complex which includes the ventrolateral, ventromedial, and ventrobasal nuclei; the intralaminar nuclei which include central medial, central lateral, paracentral and parafascicular nuclei; the midline nuclei which include the medioventral, paratenial, rhomboid, paraventricular, and submedial nuclei; the anterior nuclear group which include the anterodorsal, anteroventral, and anteromedial nuclei; the mediodorsal nucleus; the lateral nuclear complex including both lateral posterior and lateral dorsal; the posterior nuclear complex; the reticular nucleus; and the diencephalic-mesencephalic junction. The terminology used is based on previous studies.

Animals↗
PubMed1983

Rat medial frontal cortex: a visceral motor region with a direct projection to the solitary nucleus.

Pressure injections of the neuroanatomical tracer wheat germ agglutinin conjugated with HRP (WGA-HRP) were made into either the dorsal medulla or the medial frontal cortex of the rat. Following the brainstem injections, retrogradely labeled neurons were found in the paraventricular nucleus of the hypothalamus, central nucleus of the amygdala, insular cortex and in the infralimbic, prelimbic and anterior cingulate regions of the medial frontal cortex. The infralimbic labeling consisted of a dense band of neurons and was bilateral. Cells in the prelimbic and anterior cingulate regions were less densely packed. Following injections of WGA-HRP into the medial frontal cortex anterograde labeling in the dorsal medulla was confined to the solitary nucleus (NTS). Label was found throughout the rostro-caudal extent of the NTS and was bilateral although heavier contralaterally. The projection from the medial frontal cortex to the solitary nucleus suggests that this area of cortex may function primarily as a visceral 'motor' cortical region that may play a role in regulating autonomic activities.

Animals↗
PubMed1983

Propagation of focal cortical epileptiform discharge to the entopeduncular nucleus: effect of caudate lesions.

Single-unit recordings were made in the entopeduncular nucleus of cats which had previously undergone ipsilateral caudate lesions. During penicillin-induced epileptiform discharge from the pericruciate cortex, the percentage of responsive entopeduncular neurons in animals with a lesion was less than 20%. In a previous study in intact cats and in control experiments in the present study the percentage of responsive entopeduncular cells was more than 75%. These results indicate that propagation of epileptic discharge through the basal ganglia depends on intact pathways from the cortex to the caudate and from the caudate to the entopeduncular nucleus.

Animals↗
PubMed1983

Substantia nigra single unit activity during penicillin-induced focal cortical epileptiform discharge in the rat.

In urethane anesthetized rats single unit activity was recorded in the substantia nigra (SN) during focal cortical epileptiform discharges induced by topical application of penicillin to the cortical surface. Eighty percent of SN units responded during the cortical interictal spike discharge, 50% with an initial burst or increase in firing rate and 30% with an initial inhibition or decrease in firing rate. In view of the SN's widespread projections to thalamus and brainstem, these results suggest the SN may be a prominent element of the pathway involved in the spread and generalization of cortical epileptiform activity.

Animals↗
PubMed1982

A second forelimb motor area exists in rat frontal cortex.

Intracortical microstimulation of 40--50 points in the frontal cortex of ketamine-anesthetized rats using perpendicular penetrations has demonstrated a second forelimb area located rostrally near the frontal pole as well as confirming the existence of a more caudally located forelimb area just anterior to bregma. Cortex where neck and/or vibrissae movements were evoked separated the two forelimb areas. The rostral and caudal forelimb areas defined by microstimulation correspond with patches of corticospinal neurons labeled with HRP following injections of this tracer into the cervical enlargement. Digit movements were commonly evoked from the rostral forelimb area but were rarely elicited from the caudal forelimb area. The question of whether the rostral forelimb region is part of primary or supplementary motor cortex is not yet able to be answered.

Animals↗
PubMed1981

A simple method for glass insulating tungsten microelectrodes.

A method for insulating tungsten wires with glass by collapsing a glass capillary tube around the wire is described. A common laboratory electrode puller can be used. A new method for removing the glass from the tip using hydrofluoric acid is also described.

Animals↗
PubMed1980

Operant control of precentral neurons: control of modal interspike intervals.

The objects of these experiments were: (a) to determine modal interspike intervals (ISIs) of precentral cells involved in repetitious, gross motor movements; (b) to compare those modal ISIs to the modal ISIs of similar neurons under operant control; and (c) to determine if monkeys could change the modal ISIs of operantly controlled precentral neurons. Data were obtained from 4 monkeys conditioned to produce tonic firing of precentral neurons and one monkey trained to produce repetitious movements of the neck and contralateral limbs. Results are: (a) the modal ISIs from operantly controlled precentral units do not differ significantly from precentral neurons involved in repetitive gross motor movements; and (b) while under operant control, the monkeys cannot modify significantly the modal ISI of the majority of precentral neurons.

Animals↗
PubMed1980

Neuronal activity in chronic ferric chloride epileptic foci in cats and monkey.

The firing patterns of neurons surrounding sites of ferric chloride (FeCl3) injection were studied in 6 cats and 1 Macaca mulatta monkey. Although a few neurons fired in poorly structured bursts similar to what has been described for some neurons in alumina foci in monkeys, no well-formed bursts were recorded. In addition, EEG spikes were not recorded chronically in two cats, nor were EEG spikes recorded during corticography. We could not confirm the reliability of this preparation in cats as a model of chronic epilepsy.

Aluminum Oxide↗
PubMed1978

The effects of chronicity on burst structure in epileptogenic foci.

Pyramidal tract neurons (PTNs) from tungstic acid, cobalt and alumina gel foci in cat were studied for spontaneous and antidromically-evoked firing patterns. Specifically, the structured long-first-interval (LFI) burst was looked for. The LFI burst did occur spontaneously from PTNs in tungstic acid foci but could not be antidromically evoked. The LFI burst did not occur as often as would have bee predicted from cobalt and alumina foci, but, in foci older than 60 days, antidromically-evoked activity could be a burst which was structurally identical to those which occurred spontaneously. This data, in addition to that from acute penicillin foci, would indicate that the ability for single antidromic APs to evoke burst activity in PTNs is a function of the chronicity of the epileptic focus rather than the agent used to produce the focus.

Action Potentials↗
PubMed1978

Preparation for movement in the cat. I. Unit activity in the cerebral cortex.

Single unit activity was recorded from the 'motor' cortex of cats during performance of a forelimb flexion movement. Two classes of cortical neurons were defined with respect to the onset of electrographic activity associated with this movement. 'Early' unit, first showing changes in firing rates more than 0.5 sec prior to the movement, were found almost exclusively in the medial precruciate cortex. The lateral cortex appears to be made up almost uniformly of 'late' unit, that is, neurons whose activities are more closely related with the actual movement. The medial cortex, on the other hand, contains both 'early' and 'late' units and thus may have the additional function of participating in the neural system which is the substrate for response set.

Animals↗
PubMed1978

Preparation for movement in the cat. II. Unit activity in the basal ganglia and thalamus.

Of the movement-related units in the globus pallidus and entopeduncular nucleus 30--40% show early (more than 500 msec) onsets of their movement-related activity preceding self-initiated 'elbow'-flexing movements in cats. The medial pericruciate motor cortex and the VL-VA thalamic nuclei display similar distributions of onset times, in contrast to the lateral cruciate cortex where 97% of neurons change their activity much later. The possible significance of the early activity is discussed in relation to the notion of 'response set'. It is suggested that these data support the concept that the basal ganglia participate in the enabling and sequencing of movements rather than in directly causing them to occur.

Animals↗
PubMedDate not supplied

The effect of medial frontal cortex lesions on respiration, "freezing," and ultrasonic vocalizations during conditioned emotional responses in rats.

The effect of ventral medial frontal cortex (MFC) lesions on respiratory rate (RESP), immobility ("freezing"), and ultrasonic vocalizations (USVs) during conditioned emotional responses (CERs) was investigated. Male Sprague-Dawley rats were divided into two groups: MFC-lesioned rats (N = 11) sustained bilateral lesions of the infralimbic region of the MFC via microinjection of the neurotoxin NMDA; controls received sterile saline. Following a 2 week recovery period, all animals were differentially conditioned to two tones; a 2 mA footshock served as the unconditioned stimulus (US). The CS+tone was consistently paired with the US, while the CSr tone was randomly paired with the US. On the following day, RESP, freezing, and USVs were recorded during CER testing (no US were presented). All animals responded during the CS+ with increased RESP compared to baseline; the increase in MFC rats was significantly larger than in controls. All animals also froze at the onset of the CS+. Following the CS+, controls displayed a prolonged period of freezing (265 +/- 37 sec) and decreased RESP compared to baseline, and 92% emitted USVs. In contrast, MFC rats displayed a significantly shorter period of freezing (86 +/- 25 sec) and little or no USV; RESP remained significantly elevated throughout the remainder of the trial. These behaviors indicate a significantly altered stress response following ventral MFC lesions, implying that the MFC may be necessary for complete expression of various behavioral responses to "stressful" stimuli. The role of the MFC in emotion is also discussed.

Animals↗