The classically conditioned nictitating membrane response (NMR) of the rabbit, a simple form of associative motor learning, is crucially dependent upon the cerebellum. Discrete unilateral lesions of the cerebellar nuclei were made in 20 rabbits. Lesions of the anterior interpositus nucleus (IA) abolished NMR conditioning to light and white noise stimuli on the side of the lesion without affecting unconditional responses. Lesions of the posterior interpositus nucleus, fastigial and dentate nuclei were without effect upon NMR conditioning.

Behavioural and electrophysiological studies give differing impressions of when auditory discrimination is mature. Ability to discriminate frequency and speech contrasts reaches adult levels only around 12 years of age, yet an electrophysiological index of auditory discrimination, the mismatch negativity (MMN), is reported to be as large in children as in adults. Auditory ERPs were measured in 30 children (7 to 12 years), 23 teenagers (13 to 16 years) and 32 adults (35 to 56 years) in an oddball paradigm with tone or syllable stimuli. For each stimulus type, a standard stimulus (1000 Hz tone or syllable [ba]) occurred on 70% of trials, and one of two deviants (1030 or 1200 Hz tone, or syllables [da] or [bi]) equiprobably on the remaining trials. For the traditional MMN interval of 100–250 ms post-onset, size of mismatch responses increased with age, whereas the opposite trend was seen for an interval from 300 to 550 ms post-onset, corresponding to the late discriminative negativity (LDN). Time-frequency analysis of single trials revealed that the MMN resulted from phase-synchronization of oscillations in the theta (4–7 Hz) range, with greater synchronization in adults than children. Furthermore, the amount of synchronization was significantly correlated with frequency discrimination threshold. These results show that neurophysiological processes underlying auditory discrimination continue to develop through childhood and adolescence. Previous reports of adult-like MMN amplitudes in children may be artefactual results of using peak measurements when comparing groups that differ in variance.

Graphical abstractHighlights► Compared brain structure and function in SLI, unaffected siblings, and typical peers. ► More grey matter in SLI in the left inferior frontal cortex. ► Less grey matter in SLI in the right caudate nucleus and superior temporal cortex bilaterally. ► Functional activation was examined with an auditory covert naming task. ► Functionally, SLI had reduced activation of the left inferior frontal cortex and the superior temporal cortex bilaterally.

The nictitating membrane response (NMR) of 20 rabbits was conditioned to light and white noise conditional stimuli (CSs) using a periorbital shock unconditional stimulus (US). Unilateral lesions of the cerebellar cortex, sparing the underlying deep nuclei, were then made. Small lesions of cerebellar cortical lobule HVI abolished conditioning on the side of the lesion to both CSs leaving unconditional responses to the US intact. Larger lesions of the posterior lobe which spared HVI did not impair NMR conditioning. We conclude that cerebellar lobule HVI is essential for NMR conditioning in the rabbit. Degeneration following critical lesions of HVI was seen in a restricted region of the inferior olive - the medial part of the dorsal accessory olive and the adjoining medial part of the dorsal leaf of the principal olive. This region of the olive provides somatosensory information from the face to HVI. We suggest that HVI receives information related to the US via climbing fibres from the olive and CS information via mossy fibres from the pontine nuclei. The critical changes underlying NMR conditioning may be the association of these two inputs at the Purkinje cells of cortical lobule HVI.

We report the connections of cerebellar cortical lobule HVI in the rabbit. We have studied the anterograde and retrograde transport of wheatgerm-agglutinated horseradish peroxidase (WGA-HRP) following its injection into HVI to reveal efferent and afferent connections. All of the cases showed strong anterograde transport to the anterior interpositus nucleus (AIP) - indicating that this is the major efferent target of HVI. Retrogradely labelled cells were found in the inferior olivary, spinal trigeminal, lateral reticular, inferior vestibular and pontine nuclei. Within the olive, the medial part of the rostral dorsal accessory olive (DAO) and the adjacent medial part of the principal olive (PO) were consistently labelled in all cases. This area is known to receive somatosensory information from the face and neck. There was no projection to the hemispheral part of lobule VI from visual parts of the olive within the dorsal cap and medial parts of the medial accessory olive. Likely sources of visual and auditory information to HVI are the dorsolateral basilar pontine nuclei and nucleus reticularis tegmenti pontis, which were densely labelled in all cases. These anatomical findings are consistent with the suggestion that, during NMR conditioning, information related to the periorbital shock unconditional stimulus (US) may be provided by climbing fibres to HVI and light and white noise conditional stimulus (CS) information may be supplied by pontine mossy fibres.