Bruno Cardu

Interhemispheric integration of sensory and motor functions in agenesis of the corpus callosum.

Abstract Two siblings with total agenesis of the corpus callosum were compared with matched epileptic and normal controls on bimanual integration of kinesthetic, somesthetic and motor functions. No differences were found between acallosals and control subjects on any of the transfer tasks. However, the acallosal patients were impaired in bimanual operations with regard to speed. The deficit was more pronounced in the younger subject who also showed impairment of differentiated finger movements. Bilateral organization of speech and cross-cuing strategies could have accounted for facilitated performance on some but not all of the transfer tasks. Increased use of ipsilateral and/or subcortical pathways are a more plausible and more parsimonious explanation for the results of this study.

Rod and cone sensitivity in destriate monkeys

Photopic and scotopic spectral sensitivity of rhesus monkeys was determined before and after complete removal of the striate cortex. The monkeys were required to choose between a white and a series of monochromatic stimuli distributed throughout the visible spectrum. A modified method of limits was used to determine the psychophysical point of subjective equality at which the colored and white lights were perceived as being equally bright. The preoperative results indicated that the method of testing was appropriate to determine spectral sensitivity since the curves obtained compared favorably to the theoretical sensitivity curves. Postoperatively, the scotopic sensitivity curve was normal whereas the photopic curve was completely displaced towards the scotopic curve. The results as indicating that cone information is processed by the geniculo-striate visual system whereas the extra-striate structures receive their input mainly from the rod receptors of the retina.

Spectral Sensitivity in Primates: A Comparative Study

The aim of this research was to compare the photopic and scotopic spectral sensitivity of 2 New World monkeys which have not been previously studied (Cebus Capucinus and Lagothrix) with that of a normal trichromatic and a protanopic human S and an Old World monkey (Macaca mulatta). Spectral sensitivity was measured at different wavelengths using a modified method of limits. The results showed that the spectral sensitivity was identical for all Ss at a scotopic level. At the photopic level the normal human S and the Old World monkey also had a similar sensitivity. Both New World monkeys had a marked deficiency in the long wavelength part of the spectrum. This deficiency was comparable to that of the human protan. These results added therefore further evidence that New World monkeys are red deficient.

Short-term and long-term memory deficit following intracarotid amytal injection: further support for the memory consolidation hypothesis

To test the three main hypotheses of the human amnesic syndrome (encoding, consolidation, retrieval), we designed an original protocol for memory assessment under Amytal that included, in addition to a retrograde memory measure, both short-term and long-term anterograde memory measures. Twenty epileptic patients with SEEG-confirmed unilateral temporal lobe foci were given right and left injections on successive days. Only the long-term memory measure for material presented under Amytal was significantly related to the presence of a temporal contralateral epileptogenic focus, even if it was assessed when the hemisphere had completely recovered from the effect of Amytal. Short-term memory deficits were observed equally often after injections ipsilateral and contralateral to the epileptogenic focus, and no retrograde amnesia was observed. These results are consistent with the consolidation hypothesis.

Effects of ablations of the superior colliculi on spectral sensitivity in monkeys.

Abstract Spectral sensitivity of rhesus monkeys was determined before and after the total ablation of the superior colliculi. The hypothesis tested was that photopic spectral sensitivity would not be affected by the colliculectomy whereas the monkeys would loose scotopic sensitivity. This hypothesis was derived from the fact that photopic sensitivity is abolished in destriate monkeys and the remaining visual centers, probably the superior colliculi, only manifest scotopic sensitivity. Four normal and four colliculectomized monkeys were tested psychophysically to determine their photopic and scotopic spectral sensitivity. The results indicate that not only the control but also the experimental group have normal photopic and scotopic spectral sensitivity, thereby infirming the working hypothesis. These results are interpreted as indicating that, whereas the subcortical visual areas receive purely rod input, the geniculo-striate visual system is probably a mixed system receiving both rod and cone inputs.

SPECTRAL SENSITIVITY IN A FEMALE CEBUS GRISEUS

The photopic spectral sensitivity of one female Cebus Griseus was determined to complement published results showing that this monkey did not demonstrate the red deficiency typical of most New World monkeys. A modified method of limits was used to determine Ss perceived brightness of different monochromatic stimuli. The results suggest that this monkey might be a normal trichromat.

Pretectum and superior colliculus in object vs pattern discrimination in the monkey.

Abstract The present study was designed to investigate the role of the collicular-pretectal area in the acquisition of initial learning of pattern vs object discriminations. Naivemonkeys with massive bilateral lesions of the pretectum and superior colliculi were trained in object and pattern discrimination tasks with subsequent generalization. Results showed that lesioned monkeys (1) performs as well as normals on an object discrimination problem and on its subsequent generalization; (2) show great impairment in acquiring an initial pattern discrimination as well as generalizing this task; (3) demonstrate greater difficulty than normals in shifting from tridimensional objects to patterns. These results lead to the conclusion that massive midbrain lesions affect discrimination of patterns leaving intact the capacity of discriminating objects.

Effects of striatectomy and colliculectomy on achromatic thresholds in the monkey

Abstract The differential achromatic thresholds at photopic and scotopic levels of illumination were determined with normal, destriate and colliculectomized rhesus monkeys in order to evaluate the effects of removal of these 2 sets of neural structures on this primitive visual function. The discriminanda were achromatic patches subtending approximately 3.5 to 10° of visual angle. The main hypothesis was that their removal would result in a marked increase in the differential threshold though not necessarily to the same degree. This hypothesis was confirmed in the case of striate cortex removal, since the operation produced a threefold increase in threshold. The collicular ablations did not give as conclusive results since threshold increased in nearly all cases but only slightly. A second hypothesis was that the cortical ablation would affect photopic thresholds more than scotopic thresholds since the cortex had been postulated as being the only structure receiving cone input. This hypothesis was not confirmed since both photopic and scotopic thresholds increased to approximately the same extent.

MEMORY AND RIBONUCLEIC ACID (RNA): TRANSFER OF AN AVOIDANCE RESPONSE

4 groups of rats were used to test the hypothesis that learning can be “transferred” by means of “ribonucleic” acid (RNA). The experimental group was injected with RNA obtained from the brains of rats conditioned to an avoidance response. The control group received no RNA. A second control group was given RNA which came from the brains of non-conditioned rats. The fourth group received RNA extracted from the muscles of conditioned rats. The results did not confirm the transfer hypothesis since no RNA facilitating effect on subsequent avoidance training was observed.