Abstract
The rhinal cortices, such as the perirhinal cortex (PC) and the entorhinal cortex (EC), are located within the bidirectional pathway between the neocortex and the hippocampus. Physiological studies indicate that the perirhinal transmission of neocortical inputs to the EC occurs at an extremely low probability, though many anatomical studies indicated strong connections exist in the pathway. Our previous study in rat brain slices indicated that an increase in excitability in deep layers of the PC/EC border initiated the neural activity transfer from the PC to the EC. In the present study, we hypothesized that such changes in network dynamics are not incidental observations but rather due to the plastic features of the perirhinal network, which links with the EC. To confirm this idea, we analyzed the network properties of neural transmission throughout the rhinal cortices and the plastic behavior of the network by performing a single-photon wide-field optical recording technique with a voltage-sensitive dye (VSD) in mouse brain slices of the PC, the EC, and the hippocampus. The low concentration of 4-aminopyridine (4-AP; 40 μM) enhanced neural activity in the PC, which eventually propagated to the EC via the deep layers of the PC/EC border. Interestingly, washout of 4-AP was unable to reverse entorhinal activation to the previous state. This change in the network property persisted for more than 1 h. This observation was not limited to the application of 4-AP. Burst stimulation to neurons in the perirhinal deep layers also induced the same change of network property. These results indicate the long-lasting modification of physiological connection between the PC and the EC, suggesting the existence of plasticity in the perirhinal-entorhinal network.
Highlights
The perirhinal cortex (PC) is a polymodal association area that communicates with neocortical and subcortical areas, such as the sensory, temporal, and insular cortical areas as well as the amygdala, basal ganglia, raphe nucleus, and olfactory bulb (Suzuki, 1996; Kealy and Commins, 2011)
The stability of the experimental system enabled us to investigate the dynamics of neural transmission via the ‘‘gate’’ in the PC/entorhinal cortex (EC) over a long time period and contributed to new findings
Once neural propagation across the perirhinal/entorhinal border was elicited, the network property was changed, and perirhinal neural activity propagated to the EC even after 4-AP washout
Summary
The perirhinal cortex (PC) is a polymodal association area that communicates with neocortical and subcortical areas, such as the sensory, temporal, and insular cortical areas as well as the amygdala, basal ganglia, raphe nucleus, and olfactory bulb (Suzuki, 1996; Kealy and Commins, 2011). Various lesion studies have confirmed that the association between the PC and other brain regions is necessary for fear learning The PC operates in conjunction with the hippocampus via the EC, especially when spatial or contextual cues are relevant during encoding of object information (Dere et al, 2007). The one-trial object recognition test, which examines preference behavior for a novel object without reinforcement stimuli, suggests that the PC is especially critical for the encoding of object information and the maintenance of the object memory trace (Winters and Bussey, 2005). Hippocampal lesions have only revealed impairments when behavioral trials are performed in a complex spatial environment (Winters et al, 2004; Forwood et al, 2005)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call