Parallel organization of the avian sensorimotor arcopallium: Tectofugal visual pathway in the pigeon (Columba livia).

The sensory-motor division of the avian arcopallium receives parallel inputs from primary and high-order pallial areas of sensory and vocal control pathways, and sends a prominent descending projection to ascending and premotor, subpallial stages of these pathways. While this organization is well established for the auditory and trigeminal systems, the arcopallial subdivision related to the tectofugal visual system and its descending projection to the optic tectum (TeO) has been less investigated. In this study, we charted the arcopallial area displaying tectofugal visual responses and by injecting neural tracers, we traced its connectional anatomy. We found visual motion-sensitive responses in a central region of the dorsal (AD) and intermediate (AI) arcopallium, in between previously described auditory and trigeminal zones. Blocking the ascending tectofugal sensory output, canceled these visual responses in the arcopallium, verifying their tectofugal origin. Injecting PHA-L into the visual, but not into the auditory AI, revealed a massive projection to tectal layer 13 and other tectal related areas, sparing auditory, and trigeminal ones. Conversely, CTB injections restricted to TeO retrogradely labeled neurons confined to the visual AI. These results show that the AI zone receiving tectofugal inputs sends top-down modulations specifically directed to tectal targets, just like the auditory and trigeminal AI zones project back to their respective subpallial sensory and premotor areas, as found by previous studies. Therefore, the arcopallium seems to be organized in a parallel fashion, such that in spite of expected cross-modal integration, the different sensory-motor loops run through separate subdivisions of this structure.

Multizonal Cerebellar Influence Over Sensorimotor Areas of the Rat Cerebral Cortex.

The cerebral cortex requires cerebellar input for optimizing sensorimotor processing. However, how the sensorimotor cortex uses cerebellar information is far from understood. One critical and unanswered question is how cerebellar functional entities (zones or modules) are connected to distinct parts of the sensorimotor cortices. Here, we utilized retrograde transneuronal infection of rabies virus (RABV) to study the organization of connections from the cerebellar cortex to M1, M2, and S1 of the rat cerebral cortex. RABV was co-injected with cholera toxin ß-subunit (CTb) into each of these cortical regions and a survival time of 66-70 h allowed for third-order retrograde RABV infection of Purkinje cells. CTb served to identify the injection site. RABV+ Purkinje cells throughout cerebellar zones were identified by reference to the cerebellar zebrin pattern. All injections, including those into S1, resulted in multiple, zonally arranged, strips of RABV+ Purkinje cells. M1 injections were characterized by input from Purkinje cells in the vermal X-zone, medial paravermis (C1- and Cx-zones), and lateral hemisphere (D2-zone); M2 receives input from D2- and C3-zones; connections to S1 originate from X-, Cx-, C3-, and D2-zones. We hypothesize that individual domains of the sensorimotor cortex require information from a specific combination of cerebellar modules.

Brain acetylcholinesterase activity in Wistar and August rats with low and high motor activity (a cytochemical study).

Acetylcholinesterase activity was quantitatively evaluated by cytochemical method in brain structures (layers III and V of the sensorimotor cortex, caudate nucleus, nucleus accumbens, hippocampus CA3 field) of August and Wistar rats demonstrating high and low motor activity in the open field test. In August rats, acetylcholinesterase activity in the analyzed brain structures prevailed in animals with high motor activity in comparison with rats with low motor activity. In Wistar rats, the differences between the animals demonstrating high and low motor activity were less pronounced, but varied depending on the experimental series of studies. Comparisons of August rats with low motor activity and Wistar rats with high motor activity (maximum difference of motor function in these animals) revealed significant excess of acetylcholinesterase activity in layer III of the sensorimotor cortex in August rats and no differences in other brain structures of the examined animals.