Biomedical subjects

Bibiana Scelfo

Publications and source records attributed to Bibiana Scelfo.

4 recordsLinked to original sources

PubMed2005

Correlation between multiple climbing fibre regression and parallel fibre response development in the postnatal mouse cerebellum.

At the neuromuscular junction elimination of supernumerary synaptic connections during development is owing to a competitive process between single neuronal populations, whereas in the central nervous system the interaction of different types of input could affect the process. In the cerebellum, the regression from multiple- to mono-innervation of the Purkinje cells by climbing fibres is virtually completed during the first two weeks of postnatal development. While it is clear that parallel fibres are important in the control of the regression, there are conflicting results in relation to whether an early phase of regression is independent of parallel fibre effects. We studied the precise timing of climbing fibre synapse development and decline and the relationship with the functional maturation of parallel fibres. Until postnatal day (P) 6 or 7, the synaptic currents generated by different climbing fibres become progressively more uniform in amplitude. However, between P7 and 14, the amplitudes of the currents increasingly diverge until only one fibre remains connected. These data are taken as evidence that, in multiply innervated Purkinje cells, competition between different climbing fibres appears at P7 and continues during the second postnatal week. Morphological and electrophysiological data demonstrate that parallel fibres synapses appear at P7 and their development is significantly correlated with the time course of the climbing fibre regression. These results provide no evidence for climbing fibre regression independent of parallel fibres before P7 and also suggest a dominant role of the parallel fibre input in the later phase.

Age Factors↗

PubMed2005

The cerebellum: synaptic changes and fear conditioning.

In addition to coordinating movement, the cerebellum participates in motor learning, emotional behavior, and fear memory. Fear learning is reflected in a change of autonomic and somatic responses, such as heart rate and freezing, elicited by a neutral stimulus that has been previously paired with a painful one. Manipulation of the vermis affects these responses, and its reversible inactivation during the consolidation period impairs fear memory. The neural correlate of cerebellar involvement in fear consolidation is provided by a behaviorally induced long-term increase of synaptic efficacy between parallel fibers and a Purkinje cell. Similar synaptic changes after fear conditioning are well documented in the amygdala and hippocampus, providing a link between emotional experiences and changes in neural activity. In addition, in hotfoot mice, with a primary deficiency of parallel fiber to Purkinje cell synapse, short- and long-term fear memories are affected. All these data support the idea that the cerebellum participates in fear learning. The functional interconnection of the vermis with hypothalamus, amygdala, and hippocampus suggests a more complex role of the cerebellum as part of an integrated network regulating emotional behavior.

Animals↗

PubMed2004

Long-term synaptic changes induced in the cerebellar cortex by fear conditioning.

To better understand learning mechanisms, one needs to study synaptic plasticity induced by behavioral training. Recently, it has been demonstrated that the cerebellum is involved in the consolidation of fear memory. Nevertheless, how the cerebellum contributes to emotional behavior is far from known. In cerebellar slices at 10 min and 24 hr following fear conditioning, we found a long-lasting potentiation of the synapse between parallel fibers and Purkinje cells in vermal lobules V-VI, but not in the climbing fiber synapses. The mechanism is postsynaptic, due to an increased AMPA response. In addition, in hotfoot mice with a primary deficiency of the parallel fiber to Purkinje cell synapse, cued (but not contextual) fear conditioning is affected. We propose that this synapse plays an important role in the learned fear and that its long-term potentiation may represent a contribution to the neural substrate of fear memory.

Animals↗

PubMed2003

Sodium imaging of climbing fiber innervation fields in developing mouse Purkinje cells.

Maturation of specific neuronal connections in the mature nervous system includes elimination of redundant synapses formed earlier during development. In the cerebellum of adult animals, each Purkinje cell (PC) is innervated by a single climbing fiber (CF). In early postnatal development each PC is innervated by multiple CFs and elimination of synapses formed by supernumerary CFs occurs until monoinnervation is established at around postnatal day 20 (P20) in mice. It is not clear whether multiple CFs, or only a single CF, translocate from the cell body of immature PCs to the developing dendrite and, in case several CFs translocate, whether they share or segregate their innervation fields. To localize CF innervation fields, we imaged changes in postsynaptic sodium concentration resulting from CF-mediated postsynaptic currents. We found that more than one CF translocates from an innervation field on the cell body of the PC to the developing dendrite and that these CFs share rather than segregate their innervation fields. We concluded that both the soma and the proximal dendrite of the PC are territories of competition for the developing CFs and that the overlapping of their termination fields may be the prerequisite for a local process of elimination of all but one CF, as previously demonstrated in the developing neuromuscular junction.

Aging↗