Age-dependent appearance of an insulo-parietal cortical signal propagation that elicits a synchronized population oscillation in the parietal cortex in rats
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Published on: July 1, 2018
Hiroshi Yoshimura1, Nobuo Kato, Tokio Sugai
1Department of Oral and Maxillofacial Surgery, Kanazawa Medical University, Uchinada-cho, Kanazawa 920-0293, Japan. hyoshimu@kanazawa-med.ac.jp
Insights
The gustatory insular cortex and parietal cortex become functionally connected during early postnatal development in rats. This connection, crucial for sensory processing, relies on NMDA and ryanodine receptors.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Sensory Systems
Background:
- The gustatory insular cortex processes taste information.
- The parietal cortex is involved in somatosensory processing, including oral stimulation.
- Understanding the development of functional connectivity between these areas is key to understanding sensory integration.
Purpose of the Study:
- To investigate the postnatal development of functional connectivity between the gustatory insular cortex and the parietal cortex in rats.
- To determine the role of NMDA and ryanodine receptors in the formation of this functional linkage.
Main Methods:
- Electrophysiological recordings of field potentials in rat cortical slices (postnatal days 9-35).
- Stimulation of the insular cortex to evoke responses in both insular and parietal cortices.
- Pharmacological manipulation using thapsigargin and AP5 to block NMDA and ryanodine receptors.
Main Results:
- In mature rats, insular stimulation evoked a solitary potential and a subsequent population oscillation in the parietal cortex.
- In immature rats, insular stimulation failed to evoke responses in the parietal cortex.
- The parietal oscillation in mature rats was abolished by thapsigargin or AP5, while the initial potential remained.
- In immature rats, low Mg(2+) enabled responses, which were blocked by thapsigargin or AP5, indicating receptor dependence.
Conclusions:
- The insular and parietal cortices are anatomically connected but functionally unlinked in early postnatal life.
- A functional linkage dependent on NMDA and ryanodine receptors develops within the first postnatal month.
- This developmental process is critical for integrating gustatory and somatosensory information.
Abstract:
We investigated postnatal development of a functional connectivity from the gustatory insular cortex to the parietal cortex, which is known to contain many more neurons responding to oral somesthetic stimulation than the insular cortex, in slices obtained from 9-35-day-old rats. Field potentials were evoked by stimulation to the insular cortex. In the mature cortex, insular stimulation elicited a solitary field potential in both the insular and parietal cortices and, as the simulation continued, the initial solitary potential came to be followed by a population oscillation of field potential in the parietal cortex, but not in the insular cortex. In the immature cortex, by contrast, insular stimulation failed to evoke both the initial solitary potential and the subsequent population oscillation in the parietal cortex. In the mature cortex, application of neither thapsigargin nor AP5 prevented elicitation of the initial solitary potential in the parietal cortex, but either of them abolished the parietal oscillation. In immature cortex bathed with low Mg(2+) medium, insular stimulation elicited both the initial solitary potential and the subsequent parietal oscillation, which were both prevented by thapsigargin or AP5. Theses results suggest that the insular and parietal cortices are anatomically connected but functionally unlinked at an early postnatal stage, and that a functional linkage, dependent both on NMDA and ryanodine receptors, is formed during the first postnatal month.
