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Biomedical subjects

S Squatrito

Publications and source records attributed to S Squatrito.

At least 55 records · Page 3Linked to original sources
PubMed1984

Single unit activity and visual perception of motion.

Extracellular recordings were carried out in the primary visual cortex of behaving macaque monkeys. Neurons were activated by moving a visual stimulus across their receptive fields during steady fixation and by moving their receptive fields (by visual tracking) at the same velocity across a stationary visual stimulus. Out of a total number of 123 cells studied, 111 were activated by the visual stimulation both during fixation and tracking. The remaining 12 cells showed good response during fixation and very weakened response during tracking. Our results show that a small percentage of striate neurons in macaque monkey could discriminate between the real motion of an object in the visual world and the self-induced displacement of its retinal image.

Animals↗
PubMed1984

'Real-motion' cells in the primary visual cortex of macaque monkeys.

Extracellular recordings were carried out in the primary visual cortex of behaving macaque monkeys. Neurons were activated by moving a visual stimulus across their receptive fields during periods of steady fixation and by moving their receptive fields (by visual tracking) across a motionless visual stimulus, taking care that the velocities of stimulus and eye movements were the same. The total cell population (108 neurons) ws divided into 3 groups according to the cell sensitivity to visual stimulus orientation (non-oriented cell and oriented cells) and to the presence or absence of antagonistic areas in in the receptive fields (oriented cells with antagonistic areas). All the non-oriented cells (n = 14) showed almost the same response to visual stimulation both during steady fixation and during visual tracking. Out of a total number of 86 oriented cells, 77 turned out to be activated by the visual stimulation both during fixation and tracking. Eight oriented cells gave a very weak response or no response at all to visual stimulation during smooth pursuit eye movements and one neuron of the same group showed a greater response during visual tracking than during fixation. Six out of 8 oriented cells with antagonistic areas showed almost the same response to the two types of visual stimulation, while the remaining two neurons showed very weak responses during smooth pursuit eye movements. Our results show that a small percentage (about 10%) of striate neurons in macaque monkeys gave very different responses to the same physical stimulation at retinal level, according to the presence or absence of slow eye movements (smooth pursuit eye movements). The activity of these neurons seems to be related to the real movement of something in the visual world, in spite of the retinal image movement per se.

Animals↗
PubMed1984

Microprocessor-based system for spike and eye-movement data acquisition and storage.

A simple system for simultaneous recording of eye position and spike activity during on-line experimentation is described. The system is based on a relatively inexpensive and widely distributed personal computer. While the hardware is configured from commercially available products, the software has been developed in our laboratory. Data acquisition is controlled by a few routines whose logic is outline, together with the main limitations and the possible improvements of the system itself.

Animals↗
PubMed1984

Projections from the cortex of the superior temporal sulcus to the dorsal lateral geniculate and pregeniculate nuclei in the macaque monkey.

Cortical projections from the visual region and adjacent polysensory region of the superior temporal sulcus (STs) to the lateral geniculate body (LGb) were investigated in the macaque monkey using an autoradiographic tracing method. Solutions of tritiated aminoacids were injected into different parts of the caudal half of the STs of five animals. A survival time of 7 days was allowed. Labels were found in both subdivisions of the LGb: the dorsal lateral geniculate nucleus (DLGn) and the pregeniculate nucleus (PGn). In particular, part of the visual cortical region adjacent to the middle temporal area (MT) projects into the DLGn as well as the PGn, whereas the MT itself and the superior temporal polysensory region project into the PGn only. Afferents to the DLGn terminate in the magnocellular layers and in their adjoining interlaminar zones, completely sparing the parvocellular layers. Afferents to the PGn terminate in separate regions of this nucleus; the MT and adjacent visual cortices project into the internal layer of the PGn, whereas the polysensosy region of the STs projects into the external retinorecipient layer of the PGn. Possible functional implications of these projections are discussed.

Animals↗
PubMed1983

Non-oriented cells of the striate cortex activated during smooth pursuit eye movements and steady fixations in behaving monkeys.

Extracellular recordings were carried out in the primary visual cortex of behaving monkeys. Neurons were activated by moving a visual stimulus on their receptive fields during periods of steady fixation and by moving their receptive fields (smooth pursuit eye movements) on a motionless visual stimulus. Regarding non-oriented cells, they turned out to be activated by the visual stimulation both during steady fixations and smooth pursuit eye movements. Therefore, the non-oriented cells we studied seem not to receive an extraretinal signal related to the slow eye movements.

Animals↗
PubMed1983

Reproductive hormone studies in three subjects with a Robertsonian translocation.

The reproductive hormone function was investigated in three subjects, two brothers and one unrelated patient, with a Robertsonian translocation, who had come to us because of infertility. Basal levels of LH, FSH, testosterone, 17-beta-estradiol and prolactin were repeatedly measured by radioimmunoassays. In addition, clomiphene citrate, synthetic LH-RH, hCG and TRH tests were carried out. Karyotypes complemented by G-banding and C-banding, repeated semen analyses, and testicular biopsies were also obtained. The karyotype of all three subjects was 45, XY-13, -14, +t(13; 14) (p11; q11). Semen analyses showed oligozoospermia, and reduced or reduced/normal sperm motility. In addition, a high percentage of atypical forms was present in all three subjects. Reproductive hormone measurements in our three patients were substantially normal. Only one of the two brothers exhibited slightly low LH and testosterone levels. Both brothers also had elevated estradiol levels. Gonadotropin and testosterone responses to respective provocative stimuli, as well as prolactin elevation following TRH, were normal. In conclusion, the semen abnormalities observed in these three subjects with Robertsonian translocation appear to be responsible for their impaired fertility. However, the reason why some carriers of the same translocation are fertile and some others are subfertile or infertile remains unclear. It might be speculated that an individual genetic variability is responsible for different degrees of spermatogenic failure, accompanied, in more severe cases, also by reproductive hormone disorders.

Adult↗
PubMed1983

Projections from the visual cortical region of the superior temporal sulcus to the striatum and claustrum in the macaque monkey.

Solutions of tritiated aminoacids were injected into the visual cortical region hidden in the depth of the superior temporal sulcus (STs) of the macaque monkey. Injection sites involved the middle temporal visual area, extending into the surrounding visual cortices. Projections were found homolaterally in both the striatum and claustrum. In the caudate nucleus labeled material affected mainly the body and spread both to the tail and the head of the nucleus. Label was also seen in the caudal third of the putamen and in the postero-ventral claustrum. Compared with the scarcity of afferents arising from occipital visual areas, the present data point to a heavy projection system from additional visual areas of the STs to the basal ganglia in the macaque monkey.

Animals↗
PubMed1982

Bilateral projections from the visual cortex to the striatum in the cat.

Direct projections from visual areas 17, 18, 19, and lateral suprasylvian visual area (LS) to the striatum were searched for in 12 adult cats using the autoradiographic technique to detect neuronal pathways. Striatal labels were found only after injections in areas 19 and LS. Projections homolateral to the injection sites were observed from both areas to the head and body of the caudate nucleus and to the putamen. Contralateral projections were found from both areas 19 and LS: however, area 19 did not project to the contralateral putamen. The extent of contralateral projections was smaller and they were confined within the same regions as the homolateral ones. Silver grains were often arranged in cluster-like patches, which were more evident ipsilaterally, in the head of the caudate nucleus and after injections in area LS. The present data support the view of a not strictly topographical segregation of striatal projections from the cat visual cortex.

Animals↗
PubMed1982

Corticopontine projections from the visual area of the superior temporal sulcus in the macaque monkey.

1. The projections from the superior temporal sulcus (STS) visual area to pontine nuclei were studied in the macaque monkey by the autoradiographic tracing method. Microinjections of a mixture of L-[5-3H] proline and L-[4,5-3H] leucine were carried out in the posterior band and the floor of the caudal half of the STS. Survival time was always 7 days. 2. The STS visual area projects to the dorsolateral part of ipsilateral pontine nuclei. Terminal projections are distributed in patches in the whole rostro-caudal extent of the pons. 3. These findings support the view that the STS visual area in the macaque monkey is homologous to the postero-medial lateral suprasylvian area in the cat.

Animals↗
PubMed1981

Cortical visual input to the orbito-insular cortex in the cat.

The anatomical pathways supplying the visual signal to the cat orbito-insular cortex (OIC) from primary visual areas were studied by an anterograde axonal transport technique. L-[5-3H]proline was injected, in different animals, in each of areas 17, 18, 19 and the lateral suprasylvian visual area (LS). Serial histological sections were processed by autoradiographic technique after long (8-16 days) or short (30 h) survival times. The axonal flow labelled direct pathways from LS to the ipsilateral orbital gyrus and the ventral bank of the anterior ectosylvian sulcus; this region seems to correspond to that from which many authors recorded photically evoked potentials. Long survival animals injected in LS showed labels also in the contralateral OIC. No axonal flow could be demonstrated from areas 17, 18 and 19 to OIC, either at short of long survival times. The results suggest that, apart from possible sub cortical afferences, a critical visual input may reach OIC from the extrageniculostriate visual system through LS. The functional relevance of extrastriate input to OIC is discussed.

Afferent Pathways↗
PubMed1981

Bilateral cortical projections from cat visual areas 17 and 18. An autoradiographic study.

Associated and commisural connections of visual areas 17 and 18 were studied in the light of the latest knowledge about the anatomo-functional organization of the cat's visual cortices. Injections of L-[5-3H] proline were placed, in different animals, in area 17 or 18 of the right hemisphere. Serial histological sections of the whole brain were processed by autoradiographic technique, after long (8-16 days) or short (30 hours) survival times. Cortical areas labelled by axonally transported radioactive material were then correlated with electrophysiological and cytoarchitectonical maps. Areas 17 and 18 were found to send associational projections to area 19, to the anterior and posterior subdivisions of the lateral suprasylvian visual area and to two regions lying on the crown of the suprasylvian gyrus (areas 21A and 20). In addition, area 18 sends projections to ipsilateral areas 17, 7 and 5. Contralaterally, projections from areas 17 and 18 reach the homonymous areas near the margin of the other. Homotopical callosal connections of area 17 affect the band of the contralateral 17 in which part of the ipsilateral visual hemi-field is represented. Heterotopical commisural projections from the areas studied affect areas 19 and LS in regions adjoining the central vertical meridian representations. These results suggest that, on an anatomical basis, the interactions between the cortical targets of the classical geniculo-striate and the estrageniculo-striate systems are more complicated than previously believed. Furthermore, the geniculo-striate system supplies some visual input to non-visual areas through area 18.

Animals↗
PubMed1981

An autoradiographic study of bilateral cortical projections from cat area 19 and lateral suprasylvian visual area.

Associational and commissural connections of area 19 and of the lateral suprasylvian visual area (LS) of the cat were studied by means of an axonal anterograde transport technique. Multiple injections of L-[5-3H] proline were placed, in different animals, in area 19 and in two different subdivisions of LS (PMLS, PLLS). Serial histological sections of the whole brains were processed by autoradiographic technique after long (8-12 days) and short (30 hrs) survival times. Cortical areas labelled by accumulation of radioactive material were correlated with electrophysiological and cytoarchitectonic maps of cortical areas. Results showed a number of projections of areas 19 and LS not previously described. Area 19 sends ipsilateral projections to area 5 and to the medial bank of the anterior suprasylvian sulcus. The postero-medial (PMLS) and postero-lateral (PLLS) subdivisions of LS project to ipsilateral areas 5, 6, 7, 20, 21, 35, to the suprasylvian fringe (SF), to the cingulate gyrus and to the insular cortex. Contralaterally, new projections are found from area 19 to areas 20 and 5, and from LS to areas 19, 20, 21, 5, 7, SF to the cingulate gyrus and to the insular cortex. Results lead to conclude that the intra-modal and cross-modal interactions between cortical areas processing visual input are more complicated than previously assumed. The crucial role of the cat's LS in the cortico-cortical distribution of the visual message in emphasized.

Animals↗
PubMed1981

Contralateral tectal projections from single areas of the visual cortex in the cat.

1. The projections from cat cortical visuals areas to the contralateral superior colliculus (SC) were studied by the autoradiographical tracing method. Microinjections of L- [5-3H] proline were carried out in cortical visual areas 17, 18, 19 and the lateral suprasylvian visual area (LS) in different cats. Only one cortical area was injected in each animal. Survival times of 30 hours or 8 days were allowed. 2. Areas 17, 18, 19 and LS send projections to laminae, I, II and III of the frontal pole of the contralateral SC. Areas 19 and LS project also the contralateral pretectal nuclei, mainly to the posterior pretectal nucleus. 3. Cortical fibres reaching the contralateral SC pass through the brachium of the ipsilateral SC. They run along the caudal part of this structure, cross the midline and then run along the caudal part of the contralateral SC; finally, they turn anterolaterally and reach the rostal part of SC. This pathway is the tectal semidecussation (5). Cortical fibres from LS (in particular from PLLS; 15) reach the contralateral SC also via the commissure of SC. 4. Our data support the suggestion (3) that the frontal poles of SC, in the cat, may subserve straight-ahead attention and orientation to visual stimuli.

Animals↗
PubMed1980

Autoradiographic evidence for projections from cortical visual areas 17, 18, 19 and the Clare-Bishop area to the ipsilateral claustrum in the cat.

Projections from different visual areas of the cerebral cortex to the ipsilateral claustrum have been investigated in the cat by intracortical injections of [3H]proline. As a consequence of axonal flow an accumulation of radioactive material within a dorso-caudal region of the ipsilateral claustrum was found. The proline-transporting terminal arborizations of projections from areas 17, 18, 19 and the Clare-Bishop area overlap in the same claustral region. No point-to-point relation was observed between any one visual area and its claustral projection. Differences in the terminal distribution pattern were detectable according to the visual areas of origin.

Animals↗
PubMed1980

Projections from the visual cortex to the contralateral claustrum of the cat revealed by an anterograde axonal transport method.

Contralateral projections from visual areas 17, 18, 19 and the Clare-Bishop area of the cerebral cortex to the claustrum have been investigated in the cat using intracortical injections of [3H]proline. Radioactive material was found in a dorsocaudal region of the contralateral claustrum. This region was homotopic with respect to that found for the ipsilateral projection from visual cortex. The contralateral connection is assumed to be a monosynaptic pathway. The pattern by which the corticofugal fibres terminate in the claustrum is quite similar to the one described for the opposite hemisphere [6].

Animals↗
PubMed1980

Measurement of reverse triiodothyronine in dried blood spot: methodology and clinical application as a screening procedure for detection of congenital hypothyroidism.

A new sensitive radioimmunoassay method for measuring reverse triiodothyronine (rT3) concentrations in dried blood samples, designed to screen newborn infants for congenital hypothyroidism, has been developed. Paper strips are impregnated with cord blood and dried. Duplicate 5-mm diameter discs are punched from the paper strips and added directly to the radioimmunoassay reaction mixture. After incubation, bound and free hormone are separated by dextran-coated charcoal. The disc remains in the solution throughout the procedure and the assay can be completed within 24 hr. Recovery of rT3 is greater than 95% and coefficients of variation are 9.4% (intraassay) and 12.2% (interassay) at an rT3 concentration of 220 ng/dl. At very low rT3 concentrations (25 ng/dl), coefficients of variation are 14.2% (intraassay) and 18.7% (interassay). The method readily detects 12.5 ng/dl of rT3. With this paper disc method, rT3 was measured in 38 newborns and compared with serum rT3 measured in the same subjects by a standard radioimmunoassay method. The correlation between rT3 values measured in dried blood disc and in serum was very high (r = 0.918). The rT3 in dried blood discs from the cord blood of 745 normal newborns was 228.9 +/- 76.0 ng/dl (mean +/- SD). In contrast, two infants with proven congenital hypothyroidism had rT3 values of 35 and 75 ng/dl, respectively. This study indicates that rT3 can be easily measured in dried blood discs and suggests that the described method may be a useful screening procedure in a program for the detection of neonatal hypothyroidism.

Congenital Hypothyroidism↗
PubMed1980

Autoradiographic evidence of visual cortical projections to the frontal cortex in the cat.

In II adult cats, areas 17, 18, 19 as well as the lateral suprasylvian area were separately injected with L-[5-3H] proline and their efferent projections to the frontal cortex were autoradiographically searched. Only area 19 and lateral suprasylvian area showed such projections; terminal sites were localized in the ventral and dorsal banks of the cruciate sulcus and in the adjacent mesial surface of the brain. The possibility that these labeled regions may correspond to the monkey's frontal eye field is discussed.

Animals↗