Cortical intrinsic circuits can support activity propagation through an isofrequency strip of the guinea pig primary auditory cortex.
A pure tone evokes propagating activities in a strip of the primary auditory cortex (AI), an isofrequency strip (IS). A fundamental issue concerns the roles that thalamocortical input and intracortical connectivity play in generating the activities. Here we addressed this issue in guinea pigs using in vivo and in vitro real-time optical imaging techniques. As reported previously, tone-evoked activity propagated dorsoventrally along a strip (an IS) in AI. We found that an electrical pulse applied focally within the strip, triggered activity propagation with a spatiotemporal pattern highly similar to tone-evoked activation. The propagation velocity of electrically evoked activity was significantly slower than that of tone-evoked activity, but was comparable to the velocity of lateral activity propagation in cortical slices, suggesting that the electrically evoked activity propagation in vivo is mediated by intracortical circuits. To test this notion, we lesioned the auditory thalamus chemically; in such animals, electrically evoked activity in AI was not affected, although tone-evoked activity was abolished. Further, in slices of the AI, the extent of electrically evoked activity propagation in layer II/III was significantly larger in coronal slices than in horizontal slices. Together, our results suggest that intracortical connectivity in AI enables a focally evoked activity to propagate throughout an IS.
Song
Wen-Jie
WJ
Department of Electronic Engineering, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan. song@ele.eng.osaka-u.ac.jp
Kawaguchi
Hideo
H
Totoki
Shinichiro
S
Inoue
Yuji
Y
Katura
Takusige
T
Maeda
Shinichi
S
Inagaki
Shinji
S
Shirasawa
Hiroshi
H
Nishimura
Masataka
M
D000161:Acoustic Stimulation; D000818:Animals; D001303:Auditory Cortex / Q000502:physiology*; D004396:Coloring Agents; D003627:Data Interpretation, Statistical; D004558:Electric Stimulation; D004594:Electrophysiology; D005072:Evoked Potentials, Auditory / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D006168:Guinea Pigs; D007051:Ibotenic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D009415:Nerve Net / Q000502:physiology*; D013788:Thalamus / Q000502:physiology
D004396:Coloring Agents; D018690:Excitatory Amino Acid Agonists; D007051:Ibotenic Acid