The auditory corticopontocerebellar projection in the rat: inputs to the paraflocculus and midvermis. An anatomical and physiological study

Abstract

This study investigated afferent projections to the cerebellum, in particular those from the auditory cerebral cortex. The parafloccular lobule of the rat cerebellum is shown to be a primary target for the auditory cortical information with the midvermal region being a receiving area from the inferior colliculus. The method of anterograde transport of tritiated amino acids was employed to determine projections of the auditory cortex to the pons. Autoradiography showed that the site of termination of efferents from the auditory cortex corresponds to the location of neurons that project to the paraflocculus. Histogram analysis of neuronal activity in halothane anesthetized rats was employed to determine the response characteristics of neurons in paraflocculus and midvermis following cortical and tectal electrical stimulation. In addition, unit recordings of parafloccular neurons in immobilized, locally anesthetized animals demonstrated general characteristics of the responses of these neurons to auditory field stimulation. Electrical stimulation of the auditory cortex evoked mixed, excitatory-inhibitory and pure inhibitory mossy fiber responses in 33% of neurons in the paraflocculus, with no responses evident in the midvermis. Following inferior collicular stimulation, 12.6% of the neurons in the midvermis elicited a response. Recordings from parafloccular neurons in unanesthetized, immobilized rats showed evidence for excitatory and inhibitory mossy fiber responses, following auditory field stimulation. This spectrum of basic studies establishes the existence of a pathway in which the paraflocculus is revealed as an integrating target for cortical auditory information.

Region- and Layer-Specific Activation of the Higher Order Auditory Cortex Te2 after Remote Retrieval of Fear or Appetitive Memories

“…For instance, auditory cortical outputs by passing through a cortico-pontine-cerebellar pathway arrive at the cerebellar vermis (Azizi et al 1985), another brain structure that is involved in fear learning (Ruediger et al 2011;Sacchetti et al 2002Sacchetti et al , 2004Sacchetti et al , 2009). …”

Synaptic influences of pontine nuclei on cochlear nucleus cells

“…However, although the majority of inputs to PN originate from the motor and sensorimotor cortices, the PN apparently integrate various inputs. The PN receive projections from all parts of the cortex, including the visual (Hollander et al 1979;Wiesendanger and Wiesendanger 1982a, b;Legg et al 1989) and auditory cortices (Wiesendanger and Wiesendanger 1982a;Azizi et al 1985;Knowlton et al 1993;Kimura et al 2004). In line with these observations are the findings of PN neurons responding to visual and auditory stimuli (Glickstein et al 1972;Baker et al 1976;Aitkin and Boyd 1978), as well as to stimulation of visual and auditory cortices (Potter et al 1978).…”

Participação do cerebelo no processamento auditivo

“…1) Animal studies: Most authors agreed that the cerebellar hearing area is located in lobes VI and VII of Larsell [3][4][5][6][7][10][11][12][13] . Some authors added some areas to these ones, such as lobes V and VIII of Larsell, paramedian lobe, the cerebellar hemisphere and the parafloccular lobe 6,8,9,12 .…”

“…Another important piece of data is that most authors who performed experimental studies in animals observed middle latency potentials during the performance of evoked potentials 3,5,7,8 . Such data suggests that the cerebellum acts as a collaborator in the auditory processing and in cognition, thus representing an open field for numerous research projects.…”

“…Studies regarding the organization of the auditory area in the cerebellum of animals started out during the 40's, when they observed evidences that in cats the cerebellum receives inputs from auditory, tactile and visual senses, transmitting information to the cortical pathways 3 . After that, many studies followed, most of them using electrophysiological exams; though, in different animal species, trying to establish the cerebellar auditory area and its central and peripheral connections [4][5][6][7][8][9][10][11][12][13] . Once they identified in animals these hearing-related cerebellar areas and pathways, studies were initiated in humans, aiming at determining the functions of these anatomical details.…”