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Biomedical subjects

R C Saunders

Publications and source records attributed to R C Saunders.

54 records · Page 3Linked to original sources
PubMed1990

CT-guided biopsy of metastatic sacral tumors.

Between June 8, 1985 and January 29, 1986, the authors performed five CT-guided needle biopsies of suspicious sacral lesions. In each of the five cases, these biopsies allowed the acquisition of specimens suitable for definitive pathologic diagnosis. Three cases of metastatic adenocarcinoma, one case of desmoplastic fibroma, and one case of chronic inflammatory changes were noted. In the case involving chronic inflammatory changes, subsequent open biopsy was performed, confirming the inflammatory changes and absence of neoplasm. The authors conclude that percutaneous CT-guided biopsy of sacral lesion can be performed safely and rapidly, and allows accurate diagnosis and treatment of sacral lesions.

Adenocarcinoma↗
PubMed1989

The effects of fornix transection and combined fornix transection, mammillary body lesions and hippocampal ablations on object-pair association memory in the rhesus monkey.

Cynomolgus monkeys were tested on an associative memory task in which they had to remember object-object pairings. Eight animals (4 unoperated monkeys and 4 monkeys with lesions to components of the 'hippocampal-mammillary' circuit) were trained initially on a conditional object-pair association task that was similar to simple discrimination learning, but which involved presentation of object-pairs instead of single objects. Object-pairs were made up from 4 different objects, each with an identical copy. Animals had to learn which pairings of the 4 objects were rewarded (e.g. AB or CD) and which pairings were not (e.g. AC or BD). Objects appeared as a member of both rewarded and non-rewarded pairs. After several stages of training all monkeys reached a high level of performance making greater than 90% correct choices. In a performance test the monkeys had to discriminate between 3 single objects depending on their past associations with the other objects. Animals had to choose the two objects which in initial training were rewarded as an object pair. Monkeys with the 'hippocampal-mammillary' circuit lesions learned the initial object-pair discriminations at the same rate as control monkeys. In the performance test, however, monkeys with the 'hippocampal-mammillary' circuit lesions performed at chance levels, whereas the control monkeys performed significantly better. The results demonstrate a dissociation between the 'habit' and 'mediational' memory systems for ostensibly the same object-pair associations. They also indicate an important contribution of the 'hippocampal-mammillary' circuit in nonspatial association memory.

Animals↗
PubMed1988

A comparison of the efferents of the amygdala and the hippocampal formation in the rhesus monkey: I. Convergence in the entorhinal, prorhinal, and perirhinal cortices.

This is the first in a series of papers investigating the neuroanatomical basis for the interaction of the amygdala and the hippocampal formation in the rhesus monkey. The present report focuses on the complementary and convergent projections of the amygdala and hippocampal formation to the entorhinal and perirhinal cortices. These results were obtained from complementary experiments using injections of radioactively labeled amino acids to identify the anterograde projection patterns and injections of horseradish peroxidase and fluorescent retrograde tracers to confirm the cytoarchitectonic location of the neurons of origin for each projection. The results of this investigation demonstrate that both the hippocampal formation and the amygdala project to the entorhinal and perirhinal cortices where, with a few exceptions, the major projections of each structure generally are found in different layers of the same cytoarchitecture subdivisions of the entorhinal cortex but overlap in the same layers of the perirhinal cortex. Thus, the lateral and accessory basal nuclei of the amygdala project to layer 3 of areas Pr1, 28I, 28L, and 28S, and the accessory basal nucleus projects strongly to layer 1 of these same areas. In contrast, the subiculum, prosubiculum, and subfield CA1 of the of the hippocampal formation all have a projection to layer 5 of these same areas. In area 28M, the accessory basal nucleus of the amygdala projects to layer 1, while the subiculum, prosubiculum, and subfield CA1 of the hippocampal formation all project to layer 5, and the presubiculum projects to layer 3. In addition to these complementary laminar projections, there are a few areas of laminar overlap. Thus in area 28S, both the presubiculum and the CA1 subfield project to layer 3, where the lateral and accessory basal amygdaloid nuclei also project. Similarly, in 28I there is a major projection from the presubiculum and a lighter projection from the subiculum and CA1 to layer 3, where the lateral and accessory basal nuclei also project. There is also extensive laminar overlap in the perirhinal cortex. From the amygdala, the accessory basal nucleus projects to layers 1 and 3 and the lateral basal nucleus to layers 3, 5, and 6, while from the hippocampal formation, the prosubiculum projects to layers 3, 5, and 6, and the CA1 subfield projects to layer 5. This pattern of hippocampal and amygdaloid projections to the entorhinal and perirhinal cortices indicates that these cortices constitute a region of potentially extensive interaction between the amygdala and the hippocampus.

Amino Acids↗
PubMed1988

Comparison of the efferents of the amygdala and the hippocampal formation in the rhesus monkey: II. Reciprocal and non-reciprocal connections.

The pattern of direct connections between the amygdala and the hippocampal formation in the rhesus monkey (Macaca mulatta) was delineated by using both anterograde and retrograde tract-tracing techniques. From the amygdala the accessory basal, medial basal, and the cortical nuclei and the cortical amygdaloid transition area send projections to the hippocampal formation. The efferents from the magnocellular part of the accessory basal nucleus and the cortical nuclei terminate in the molecular layer of subfields CA3, CA2, and CA1', and to a lesser extent in the molecular layer and the superficial part of the pyramidal cell layers of the prosubiculum. In contrast, the projections from the medial basal nucleus and the cortical amygdaloid transition area terminate in the molecular layer and the superficial part of the pyramidal cell layers of the prosubiculum only. From the hippocampal formation, subfield CA1' and the prosubiculum send efferents that terminate in the medial basal nucleus, the cortical transition area, and the ventral part of the cortical nuclei. In addition, the CA1' subfield projects to the ventral, parvicellular part of the accessory basal nucleus. The present data emphasize an important role for the prosubiculum and the CA1' subfield in medial temporal lobe area connections. Both regions, in addition to supporting direct connections between the amygdala and the hippocampal formation, also have extensive connections with the entorhinal cortex. As for the amygdala, the accessory basal nucleus sends efferents to both the hippocampal formation and the entorhinal cortex. The data demonstrate an anatomical means by which the amygdala, hippocampal formation, and the entorhinal cortex may interact. It is proposed that these connections may be important in the limbic memory system.

Amino Acids↗
PubMed1986

The measurement of liver blood flow in conscious calves.

Observations were made following single I.V. injections or during continuous I.V. infusions of sulphobromophthalein (BSP) in three Jersey calves (3-5 months of age) which had an indwelling hepatic vein catheter, surgically implanted under general anaesthesia. Simultaneous sampling of blood from a peripheral (jugular) vein and an hepatic vein enabled calculations of hepatic plasma flow (E.H.P.F.) based on the Fick principle. Estimates of E.H.P.F. in nine single injection experiments gave a mean flow of 38.6 ml X min-1 X kg-1 compared to 32.6 ml X min-1 X kg-1 estimated in seven continuous infusion experiments. The over-all mean haematocrit in the three calves was 30.0% and the E.H.P.F. values are equivalent to hepatic blood flows of 55 and 47 ml X min-1 X kg-1 respectively. In thirteen out of fourteen experiments the plasma clearance of BSP in jugular vein blood after a single I.V. injection of 5 mg BSP X kg-1 body weight was best fitted by a double exponential model of distribution of BSP. Parameters from these exponentials were used to calculate E.H.P.F. by the method of Clarkson, Hardy-Smith & Richards (1976) and gave values of 11.3 ml X min-1 X kg-1, clearly indicating that the method cannot be applied in conscious calves.

Animals↗
PubMed1985

Visual recognition in monkeys: effects of transection of fornix.

An earlier finding from this laboratory of only a mild recognition impairment after hippocampal removal in mature monkeys (Mishkin 1978) contrasts with the severe deficit originally reported by Gaffan (1974) following transection of the fornix in immature monkeys. Investigation of some of the methodological differences between the two studies (lesion site, age of monkeys, and behavioral paradigm) failed to resolve the discrepancy in results, only a small impairment resulting under all conditions examined. While some still unexplored differences must underlie the divergent findings, it appears that only a comparatively mild impairment in recognition memory results from damage to the hippocampal system under a wide variety of conditions.

Age Factors↗
PubMed1984

Further evidence that amygdala and hippocampus contribute equally to recognition memory.

The medial temporal neuropathology found in an amnesic neurosurgical patient [17] was simulated in monkeys in an attempt to determine whether the patient's mnemonic disorder, which had been ascribed to bilateral hippocampal destruction, may have also been due in part to unilateral amygdaloid removal. For this purpose, monkeys were prepared with bilateral hippocampectomy combined with unilateral amygdalectomy, and (as a control) bilateral amygdalectomy combined with unilateral hippocampectomy. The animals were trained both before and after surgery on a one-trial visual recognition task requiring memory of single objects for 10 sec each and then given a postoperative performance test in which their one-trial recognition ability was taxed with longer delays (up to 2 min) and longer lists (up to 10 objects). The two groups, which did not differ reliably at any stage, obtained average scores on the performance test 75 and 80%, respectively. Comparison with the results of an earlier experiment [8] indicates that this performance level lies approximately midway between that of monkeys with amygdaloid or hippocampal removals alone (91%) and that of monkeys with combined amygdalo-hippocampal removals (60%). The results point to a direct quantitative relationship between degree of recognition impairment and amount of conjoint damage to the amygdala and hippocampus irrespective of the specific structure involved. Evidence from neurosurgical cases tested in visual recognition [21] indicates that the same conclusion may apply to man.

Amygdala↗
PubMed1984

Monkeys with combined amygdalo-hippocampal lesions succeed in object discrimination learning despite 24-hour intertrial intervals.

Monkeys with combined amygdalo-hippocampal removal show severe impairments on visual memory tasks after delays of only a minute or two, yet they learn visual discrimination habits about as quickly as normal animals with intertrial intervals of the same duration. In an attempt to resolve this discrepancy between abnormally rapid forgetting and successful retention, tests were conducted to determine whether discrimination learning would be prevented in animals with limbic lesions if intertrial intervals lasted 24 hr. The results showed that as long as the lesion did not encroach on inferior temporal cortex, the operated animals could acquire concurrent sets of 20 object discrimination habits at the same rate as normal animals, in an average of about 10 trials per set. The findings suggest that learning and retention processes are divisible into a mechanism for memory formation that is dependent on the limbic system and a mechanism for habit formation that is not.

Amygdala↗
PubMed1984

Impairments of visual object transforms in monkeys.

Monkeys were first trained on a series of standard, unchanging visual objects to obtain food reward. After reaching criterion on each subject, training with it continued but on 20 per cent of the trials the object was transformed in (1) size, (2) orientation, or in (3) its shadow configuration. Monkeys with lesions either of the inferotemporal cortex or the foveal prestriate region were impaired in identifying all three types of transforms as the rewarded object. They were also slightly impaired in continuing postcriterion high levels of performance on the nontransformed objects, but it was shown that the transform deficit was still present when this factor was partialled out. The groups with transform deficits were also impaired initially in their discrimination between solid cones of varying apical angle, although their final performance approached that of controls. The inferotemporal group, especially with the lesion placed anteriorly, had a deficit in their initial learning of the untransformed objects as well as in the retention of a preoperatively learned pattern discrimination; they were also deficient in selecting food objects from among an array of nonfood objects. No deficits were seen in animals with lesions of the parietal lobe or the fundus of the superior temporal sulcus in any task. The results and other relevant animal evidence are interpreted in terms of the view that the anterior temporal lobe is concerned with the storage of an object-centred prototype, necessary in turn for the attachment of positive or negative meaning, and the more posterior inferotemporal lesions with the addressing of view-centred visual information en route to the anterior regions. They are also consistent with the findings on the recognition of 'unusual views' made by Warrington and coworkers in patients with posterior lesions.

Animals↗
PubMedDate not supplied

The relationships between temporal lobe and diencephalic structures implicated in anterograde amnesia.

The relationship between the anterograde amnesic syndromes associated with diencephalic and temporal lobe pathology is examined in the light of recent findings. It is proposed that a common feature of anterograde amnesia is damage to part of an "extended hippocampal system" comprising the hippocampus, the fornix, the mammillary bodies, and the anterior thalamic nuclei. Damage to this system results in deficits in the recall of episodic information, the core symptom of anterograde amnesia. In contrast, lesions in this system need not disrupt tests of recognition memory when they primarily tax familiarity judgements. It is assumed that familiarity judgements depend on other regions (e.g. the rhinal cortex in the case of temporal lobe amnesia) and that the extended hippocampal system is principally involved in those aspects of recognition that are retrieval-based rather than familiarity-based. These proposals arise from new evidence on the performance of delayed nonmatching-to-sample by animals, from a meta-analysis of the performance of amnesic subjects on a test of recognition memory, and from new research into the pattern of connections between the medial temporal lobe and the medial diencephalon in primates.

Amnesia↗