PubMed Health⌕ Search

Biomedical subjects

I H Wagman

Publications and source records attributed to I H Wagman.

At least 19 recordsLinked to original sources
PubMed1978

Nociceptive responses of neurons in medial thalamus and their relationship to spinothalamic pathways.

1. An extracellular study of the cat medial thalamus has revealed four types of somatosensory neurons. These were located primarily in the n. parafascicularis, n. subparafascicularis, and n. centralis lateralis; none were found in the n. centrum medianum. There was no functional segregation of neurons within each nucleus or between nuclei. Each type of neuron had large and often bilateral receptive areas. No somatotopic organization of neurons was found within the medial thalamus. 2. Noxious (N) and noxious-tap (NT) neurons comprising 72% of the sample (78 of 109 total) were considered to be nociceptive. N cells responded exclusively to noxious mechanical stimulation of skin, muscle fascia, tendons, and joints, and to direct stimulation of A-delta- and C-fiber groups in cutaneous, articular, and muscle nerves. NT cells responded to noxious and tap stimulation in a differential manner and to stimulation of the entire spectrum of A- and C-fibers. N and NT cells accurately signaled the duration of noxious mechanical stimulation. Their nociceptive responses were also graded as a function of both noxious stimulus intensity and the number of activated A-delta- and C-fibers. Stimulation of A- and C-fibers evoked, respectively, an inital burst and a late burst of discharges. A brief period of inhibition intervened between the initial and late bursts of NT cells. Prolonged afterdischarge was often observed following noxious natural stimulation or stimulation of A-delta- and C-fibers. The phenomenon of discharge "windup" was observed during iterative stimulation of C-fibers. 3. Tap (T) neurons (10%) responded only to brisk but innocuous taps applied to skin or underlying tissue. These cells were driven only by activation of A-alpha- and A-beta-fibers. The response to such stimulation was seen as an initial burst of discharges followed by an inhibitory period. 4. Inhibited (I) neurons (18%) had resting discharges that were inhibited by noxious stimuli and stimulation of A-beta- and C-fiber groups. 5. The results obtained from monitoring the peripherally evoked responses of nociceptive N and NT neurons before and after selective lesions of the spinal cord strongly suggested that the spinothalamic tracts were the only spinal projections mediating A- and C-fiber input to these cells. Each spinothalamic tract apparently carried information originating from both sides of the body.

Animals↗
PubMed1978

Nociceptive responses of neurons in the posterior group of nuclei and medial thalamus.

Anatomical studies have shown that fibers of the spinothalamic tract terminate in both the posterior group of nuclei (PO) and the nuclei of the medial thalamus. Only the PO receives fiber terminations from the spinocervicothalamic and dorsal column-medial lemniscal projections. This difference in connectively is reflected in the functional differences between the neurons in the PO and those in the medial thalamus. Although both PO and medial thalamus contain a large proportion of nociceptive neurons, only the PO contains neurons that have "lemniscal" response properties. Lesion studies have demonstrated the importance of the spinothalamic tract in mediating A and C fiber input to nociceptive neurons in the PO and medial thalamus. These studies showed that the nociceptive neurons in PO also receive A fiber input from the dorsal column-medial lemniscal projection and A and C fiber input from the spinocervicothalamic projection.

Afferent Pathways↗
PubMed1975

Relationship between growth of brain and skull of Macaca mulatta and its importance for the stereotaxic technique.

An analysis of the brain weight of 196 rhesus monkeys and lateral X-rays of 91 more was made to determine and correct the effect of growth and development on sterotaxic variability. A comparison of body weight to brain weight shows that the brain grows rapidly initially in a linear relationship with body weight and can increase in weight even into adulthood, with a significant amount of variability found throughout its development. The examination of the cranial base and sterotaxic reference points indicates that the brain rotates during growth in a forward and downward direction in relation to the sterotaxic planes. The distance between the anterior clinoid process and AP-0 shows an increase of little variability from linearity during growth. This distance can be used to correct for the anterior-posterior plane found in standard stereotaxic atlases. The flattening out of the cranial base results in a horizontal plane readjustment during growth. A horizontal correction can be made by measuring the distance between the base of the pituitary fossa and H-10 plane.

Animals↗