Olfactory perception and behaviors critically depend on the ability to identify an odor across a wide range of concentrations. Here, we use calcium imaging to determine how odor identity is encoded in olfactory cortex. We find that, despite considerable trial-to-trial variability, odor identity can accurately be decoded from ensembles of co-active neurons that are distributed across piriform co...

Denervation of the piriform cortex by bulbotomy causes a series of important cellular changes in the inhibitory interneurons of layer I and transsynaptic apoptosis of a large number of pyramidal neurons in outer layer II within 24 h. In this study, we report that following the marked loss of neurons in outer layer II, the piriform cortex is reconstituted by the addition of newly formed neurons ...

Although a major output of the hippocampal formation is from the subiculum to the deep layers of the entorhinal cortex, the parasubiculum projects to the superficial layers of the entorhinal cortex and may therefore modulate how the entorhinal cortex responds to sensory inputs from other cortical regions. Recordings at multiple depths in the entorhinal cortex were first used to characterize fie...

Associational connections of pyramidal cells in rat posterior piriform cortex were studied by direct visualization of axons stained by intracellular injection in vivo. The results revealed that individual cells have widespread axonal arbors that extend over nearly the full length of the cerebral hemisphere. Within piriform cortex these arbors are highly distributed with no regularly arranged pa...

Olfactory oscillations are pervasive throughout vertebrate and invertebrate nervous systems. Such observations have long implied that rhythmic activity patterns play a fundamental role in odor coding. Using intracranial EEG recordings from rare patients with medically resistant epilepsy, we find that theta oscillations are a distinct electrophysiological signature of olfactory processing in the...

The ability to target subclasses of neurons with defined connectivity is crucial for uncovering neural circuit functions. The olfactory (piriform) cortex is thought to generate odour percepts and memories, and odour information encoded in piriform is routed to target brain areas involved in multimodal sensory integration, cognition and motor control. However, it remains unknown if piriform outp...

We combined pharmacological studies and electrophysiological recordings to investigate modifications in muscarinic acetylcholine (ACh) receptors (mAChR) in the rat olfactory (piriform) cortex, following odor-discrimination rule learning. Rats were trained to discriminate between positive and negative cues in pairs of odors, until they reached a phase of high capability to learn unfamiliar odors...

INTRODUCTION The hippocampus and piriform cortex have a critical role in seizure propagation. In this study, the role of adenosine A1 receptors of piriform cortex on CA1 hippocampal kindled seizures was studied in rats. METHODS Animals were implanted with a tripolar electrode in the right hippocampal CA1 region and two guide cannulae in the left and right piriform cortex. They were kindled by...

The aim of the study was to investigate neurochemical changes in a kainic acid (KA; 10 mg/kg, s.c.)-induced spontaneous recurrent seizure model of epilepsy, 6 months after the initial KA-induced seizures. The neuronal markers of cholinergic and gamma-aminobutyric acid (GABA)ergic systems, i.e. choline acetyltransferase (ChAT) and glutamic acid decarboxylase (GAD) activities, and a marker for ne...

The piriform cortex is a temporal lobe structure with a very high seizure susceptibility. To investigate the spatiotemporal characteristics of epileptiform activity, slices of piriform cortex were examined by imaging electrical activity with a voltage-sensitive fluorescent dye. Discharge activity was studied for different sites of stimulation and different planes of slicing along the anterior-p...