Piero Paolo Battaglini

Cortico-cortical connections from the visual region of the superior tempora sulcus to frontal eye field in the macaque

Abstract Injections of tritiated amino acids were made in the posterior bank and the fundus of the caudal third of the superior temporal sulcus (STs) of macaque monkeys. The injection sites lay mainly within the heavily myelinated region of STs, namely the middle temporal area. Labelled material was found in the surface of the caudal-most part of the prearcuate gyrus and in the anterior bank of the arcuate sulcus, that is in a restricted region of the part of the prefrontal cortex known as frontal eye field (FEF). The possibility that FEF may include several functional units receiving different visual inputs is considered.

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].

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.

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

SummaryDirect 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.

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.

Chapter 26: Some extra-striate corticothalamic connections in macaque monkeys

Publisher Summary This chapter describes some corticothalamic connections of the middle temporal (MT) area and the neighbouring, MT-recipient, visual region situated in the fundus and upper bank of superior temporal sulcus (STS) of the macaque monkey. These connections turned out to be part of a parallel network reciprocally linking sensory structures to cortical and subcortical formations that, from anatomical and electrophysiological investigations, appear to be involved in the neural control of directionally oriented eye movements, as well as in the orientation of visual attention. In the macaque monkey, the caudal half of the STS is an important cortical station of the extrageniculo-striate visual system in which discrete visual areas have been identified. Among these, the MT area is reputed to play a key role in visual motion analysis because of the property of its neurons to selectively respond to the direction and speed of moving visual stimuli. Areas surrounding MT are less defined as to their anatomical limits, connections, and functions. The pieces of evidence highlighted in this chapter suggest that the extrageniculo-striate corticothalamic system involving the superior temporal cortex is an intimate part of a complex network of functional units.

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.

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 outlined, together with the main limitations and the possible improvements of the system itself.