Biomedical subjects

M Cattarelli

Publications and source records attributed to M Cattarelli.

At least 19 recordsLinked to original sources

PubMed2001

Cell activity in the anterior piriform cortex during an olfactory learning in the rat.

Several studies have shown that the piriform cortex is involved in learning processes and pyramidal cell activity does not only encode the odour quality but is also related to contextual information about past experience and future action. To study how odour-specific patterns in neuronal activity are established we used an odour discrimination go/no go task with water reinforcement for analysing extracellular single cell activity in anterior piriform cortex in freely moving rats. During conditioning single cells responded to different task events. Of the cells 52% participate in odour sampling and 87% were involved in odour discrimination. More than half of the responses to odours were inhibitory responses. Seventeen percent changed their activity for nose-poke only. The activity of 33% was related to reinforcement. Once established the pattern of reaction to the odour was preserved for several days. It is suggested that the anterior part of the piriform cortex is not involved in odour coding only. However, learning-related plasticity was not observed in this area.

Animals↗

PubMed2001

Expression of Fos in the piriform cortex after acquisition of olfactory learning: an immunohistochemical study in the rat.

The piriform cortex (PCx), the main area of the primary olfactory cortex, is assumed to play a role in olfactory memory. Involvement of this paleocortex in mnesic processes was investigated by using Fos immunocytochemistry after acquisition of a two-odor discrimination task. Trained rats had to associate one odor of a pair with water reward while pseudo-trained rats were randomly rewarded. We further used non-trained rats and home cage control animals to determine the effect of manipulation and basal Fos level respectively. Except in control rats, Fos immunoreactivity was mainly distributed in brain areas involved in olfactory processing, learning and arousal. The trained, pseudo-trained, and non-trained rats showed a high Fos labeling in the entire PCx. However, quantitative analysis demonstrated a statistically higher Fos immunoreactivity in the anterior PCx in comparison with the posterior PCx for these rats. Furthermore, behavioral data allowed us to distinguish two groups of trained rats according to the number of days required to acquire the task. Rats with slow acquisition showed a higher Fos immunoreactivity in the whole PCx in comparison with the rats exhibiting a fast acquisition. Our findings support the assumption of a PCx rostro-caudal heterogeneity which could sustain differential information processing.

Animals↗

PubMed1999

Modulation of the piriform cortex activity by the basal forebrain: an optical recording study in the rat.

The piriform cortex (PCx) is the main projection area of the olfactory bulb. It further receives afferents from neurons located in the horizontal limb of the diagonal band (HDB) and the magnocellular preoptic nucleus (MCPO) of the basal forebrain. Using an optical recording technique, we examined the influence of electrical stimulation of the HDB-MCPO complex upon the PCx reactivity to electrical stimulation of the olfactory bulb. We observed an inhibitory modulation which was stronger on the intrinsic activity than on the afferent one. This effect was not homogeneously distributed within the whole PCx. The neurotransmitter involved and its synaptic target remain to be determined. The present findings are discussed in view of anatomical and functional data.

Afferent Pathways↗

PubMed1999

Implications of relaxation dynamics in the synaptic control of olfactory cortex activity.

In a previous work (Ballain et al., 1998. Biol. Cyber. 79, 323-336) we reported the analysis of a model for the piriform cortex activity in rats based on experimental data. In this paper, we study an extension of this model by supplementing it with equations for the post-synaptic conductance and/or the pre-synaptic activation threshold. We use the present model's outputs to account for experimental data based on paired stimulation in the opossum or the rat, obtained either through electrical recording or optical mapping of the cortex activity. The model exhibits great robustness when it comes to large variation in synaptic characteristics. Model outputs mimic satisfactorily the three kind of responses to paired stimuli (Litaudon and Cattarelli, 1996. Eur. J. Neurosci. 8, 21-29) and the recovery of the excitable capacities as demonstrated by Haberly (1973. J. Neurophysiol. 36 (4), 789-802) and Ferreyra-Moyano et al. (1985. Brain Res. Bull. 15, 237 248).

Animals↗

PubMed1998

Role of the net architecture in piriform cortex activity: analysis by a mathematical model.

We present a mathematical analysis of the piriform cortex activity in rats. Experimental data were obtained by means of optical recording of fluorescent signals driven by neuronal activity. From these data, we determined the numerical value of the relaxation time for the pyramidal cell activity in layers II and III and the time latency map for bulb activation. Our model for the piriform cortex is based on pairs of excitatory and inhibitory neurons which correspond to pyramidal cells of layers II and III and to their inhibitory associated interneurons respectively; pyramidal cells are also interconnected through short and long range association fiber systems. Under such conditions, the model outputs resemble closely the experimental observations: (1) a double-bumped response to a strong and short stimulation; (2) oscillatory behavior under weak sustained stimulation conditions; (3) propagation of traveling activity waves; and (4) pacemaker activity when clusters of neurons are preferentially coupled.

Animals↗

PubMed1997

Evidence for synchronised responses in the piriform cortex by using Gibbs potential analysis.

The piriform cortex is a large paleocortical area which receives direct projections from the olfactory bulb. In order to study the spatiotemporal distribution of the piriform cortex activity, we chose optical recording of the responses evoked by olfactory bulb electrical stimulation. Such a stimulation elicited a large signal corresponding to cortical reactivation (disynaptic activity) via intrinsic association fibres. As the disynaptic activity was observed over the entire piriform area, we wondered whether or not this redistribution contributes to a synchronisation of the activity in the piriform cortex. In order to answer this question, we developed a statistical approach which allows us to take the temporal dimension into account. The analysis was performed by using the Gibbs potential analysis. The neural response of the diode is represented by a stochastic point process (occurrence of latency peak), and the response of the diode array is given as successive realisations of a binary random field defined on a finite set. The Gibbs measure associated with this field is then estimated through the interaction potentials of the field's configurations, which provide a quantitative evaluation of the interaction and the synchronisation between the neural sites. The analysis was performed on the latency of the peak of disynaptic activity, which was determined from signals from 60 different acquisitions realised with the same stimulus parameters. From these 60 files of latency values, we estimated the Gibbs interaction potential of singletons and pairs. The former gave an image of the spatiotemporal distribution of the disynaptic activity, which appears to propagate from the anterior to the posterior part of the area recorded. The estimation of the interaction potential of pairs allows us to characterise the degree of synchronisation between two neighbouring recording sites. It appeared that, in the anterior half of the area recorded, the disynaptic activity was statistically desynchronised whereas, in the posterior part the disynaptic activity appeared strongly synchronised. The functional implications of such a spatiotemporal distribution of the activity are discussed.

Models, Biological↗

PubMed1997

Optical recording of the rat piriform cortex activity.

The piriform cortex (PCx) is a phylogenetically old brain structure which presents characteristics of a content-addressable memory. Taking into account its particular anatomo-functional organization, we hypothesized that this cortex could behave rather as an assembly of different functional units than as a functionally homogeneous structure. This hypothesis was tested by using both anatomical and functional approaches. Immunohistological and tracing experiments demonstrated that both the connections of the PCx with the higher nervous centres, and its monoaminergic and cholinergic modulatory afferents exhibited a heterogeneous distribution. Then, optical monitoring of its neuronal activity with a voltage-sensitive dye pointed out that the PCx is a functionally heterogeneous structure. Electrical stimulations of the olfactory bulb showed that the inhibitory processes which control the cortical responsiveness were not identical in all the PCx area. Two different functional areas at least could be distinguished: in the ventromedial PCx, the afferent activity is privileged since the level of inhibition of disynaptic activation remained large during repetitive stimuli. Contrarily, in the posterior PCx, the disynaptic activity remained unchanged in response to successive stimulations and the responses of neighbouring sites were statistically more synchronized than in its anterior part. Moreover, a late depolarization wave was significantly larger in the posterior PCx. These data are in good agreement with the results provided by computational models of the PCx. In the future, theoretical and experimental investigations of this cortex will be useful for understanding olfactory information processing and as a model of brain functioning at the neocortical level as well.

Animals↗

PubMed1997

Learning-induced changes in rat piriform cortex activity mapped using multisite recording with voltage sensitive dye.

The piriform cortex (PCx) has a potential role in storage and recall of olfactory information. This study is a first extensive investigation of the spatiotemporal distribution of activity in the PCx induced by learned sensory inputs following conditioning. In a conditioned group, rats chronically implanted with four electrodes in the olfactory bulb were trained to associate the electrical stimulation of a given bulbar electrode with a positive reinforcement, while stimulation of a different electrode predicted a negative reinforcement. In a familiarized group, rats received the same protocol of daily electrical stimulation with no associated reinforcement. At the end of the conditioning or familiarization episode, activity evoked in the PCx was optically mapped using a 144 photodiode array. In the anaesthetized rats, PCx maps were recorded in response to stimulation of each of the four bulbar electrodes using either high (0.5-1 mA) or low (0.1 mA) test current intensities. Low intensity stimulation revealed that conditioning selectively enhanced the probability of occurrence of a signal composed of a single late (56-73 ms) component which occurred almost simultaneously on a large PCx area. In the conditioned group, high intensity stimulation through either of the four electrodes revealed a potentiation of the early (17-30 ms) disynaptic component of the PCx response in the most posterior part of the PCx as well as a homogeneous increase of the late (39-52 ms) component spread over the PCx areas. These data suggest that learning induces synaptic changes at different nodes of the PCx circuitry.

Animals↗

PubMed1996

Intrinsic association fiber system of the piriform cortex: a quantitative study based on a cholera toxin B subunit tracing in the rat.

By using retrograde and anterograde transport of the B subunit of cholera toxin (CTb), we examined quantitatively the association fiber systems, i.e., the collaterals of pyramidal cell axons, that reciprocally connect both the rostral and the caudal parts of the piriform cortex (PC). Well-defined CTb injections were obtained in layers Ib or II-III of the rostral and the caudal parts of the PC. Using precision counting, we determined the proportion of cellular profiles in layers II and III that gave rise to association fibers and thus demonstrated a predominance of rostrocaudal fibers over the caudorostral ones. Our data also support a precise laminar organization of the PC in which the rostrocaudal fibers originated mainly from layer II and the caudorostral fibers primarily from layer III. Cholera toxin injections into layer Ib produced a peak of labeled profiles 2 mm from the site, indicating that a large proportion of the association fibers from layer II travel for at least 2 mm and then synapse in layer Ib. At either end of the PC, the association projections with respect to olfactory processing, propagation of the activity within the PC, and the possible role of intrinsic fibers in olfactory memory.

Animals↗

PubMed1996

Catecholamine innervation of the piriform cortex: a tracing and immunohistochemical study in the rat.

In order to determine the origin of the catecholamine innervation of the rat piriform cortex (PC), we combined retrograde transport of the B subunit of the cholera toxin (CTb) with tyrosine hydroxylase (TH) immunohistochemistry. A substantial number of CTb retrogradely labeled cells was found in the parabrachial pigmented, paranigral and interfascicular nuclei of the ventral tegmental area and the dorsal part of the locus coeruleus, whereas nearly no labeling was noted in the substantia nigra. Following TH immunohistochemistry on the same sections, most if not all of the CTb labeled cells were also TH immunoreactive. Occasional double-labeled cells were also observed in the anterior part of the raphe dorsal nucleus. As visualized with dopamine beta-hydroxylase, dopamine or TH immunohistochemistry, the noradrenaline fibers were homogeneously distributed whereas the dopamine fibers showed rostro-caudal and latero-medial differences. The distribution of TH fibers overlapped both patterns. Our report suggests that the heterogeneous distribution of the DA fibers could support a differential centrifugal modulation of the olfactory information processing throughout the PC.

Animals↗

PubMed1996

Reciprocal and topographic connections between the piriform and prefrontal cortices in the rat: a tracing study using the B subunit of the cholera toxin.

In the present study, the reciprocal connections between the piriform cortex and the prefrontal areas are described on the basis of experiments using the anterograde and the retrograde transport of the cholera toxin B subunit (CTb). Following CTb injections placed in the anterior part of the piriform cortex, retrogradely labeled cells and anterogradely labeled fibers were mainly found in the ventrolateral and lateral orbital areas as well as in the anterior part of the agranular insular cortex. Following injections placed in the posterior part of the piriform cortex, the CTb labeling was primarily observed in the infralimbic area and the posterior part of the agranular insular cortex. Thus, we described a topographical organization of the direct reciprocal connections between the anterior and the posterior parts of the piriform cortex parts and some prefrontal areas. This could support a differential modulation of the olfactory processing along the rostrocaudal dimension of the piriform cortex.

Animals↗

PubMed1996

Olfactory bulb repetitive stimulations reveal non-homogeneous distribution of the inhibitory processes in the rat piriform cortex.

Optical signals were recorded in the in vivo rat piriform cortex in response to a burst of seven electrical stimulations (100 ms interval) delivered in the olfactory bulb. Based on the recorded responses, three types of signal could be identified according to the relative amplitude of their monosynaptic and disynaptic components. The dysynaptic component had a larger (type 1) or an equal amplitude (type 2) compared with the monosynaptic one. Type 3 exhibited only the monosynaptic component. Type 1 represented 96% of the first response. The second response was characterized by an increase in type 3 signals (39%). The remaining type 1 signals were lower in amplitude when compared with the first response. The responses to the last five stimulations did not differ from one another but were different from the first two (type 1, 74%; type 2, 7.8%; type 3, 18.2% on average). The spatial distribution of these three types of signal was analysed by dividing the piriform cortex into several areas. These areas were not homogeneous in the percentage of each signal type: the percentage of type 3 signals was highest (approximately 30%) in the area near the lateral olfactory tract and < 10% in the most posterodorsal area. Thus the level of inhibition remained high in some piriform areas whereas it decreased rapidly in others, suggesting that the inhibitory processes were not homogeneously distributed in the whole piriform cortex. Functional implications are discussed.

Animals↗

PubMed1995

Piriform cortex late activity revealed functional spatial heterogeneity.

Optical signals were recorded in the in vivo rat piriform cortex (PC) in response to olfactory bulb electrical stimulation. Sometimes the early response was followed by a longer latency component with an occurrence probability of 0.25. In order to compare the early and late activity, the ratio between early (disynaptic) and late wave amplitudes was measured at each recording site on the whole PC. Its spatial distribution revealed that the relative importance of the late activity was larger in the most posterior part of the PC whereas the late wave was rarely observed in the anterior PC. Such a result gave new information on the functional heterogeneity of the PC.

Animals↗

PubMed1995

Serotonergic and non-serotonergic projections from the raphe nuclei to the piriform cortex in the rat: a cholera toxin B subunit (CTb) and 5-HT immunohistochemical study.

Retrograde axonal transport of the cholera toxin B subunit (CTb) was combined with 5-HT immunohistochemistry to determine the origin of the serotonergic innervation of the piriform cortex (PC) in the rat. After iontophoretic CTb injections in the PC, a substantial number of retrogradely labeled cells were found in the middle and medio-ventral part of the dorsal raphe nucleus (RD). A few retrogradely labeled cells were also observed in the median raphe nucleus (MnR) and the B9 serotonergic cell groups. Following CTb and 5-HT immunohistochemistry on the same sections, double-labeled cells were observed in the RD, MnR and B9 groups. In the RD, 30% of CTb stained cells were immunoreactive to 5-HT. After colchicine or nialamide (a monoamine oxidase inhibitor) pretreatment the percentage of these double-labeled cells reached 70%. These results indicate that both 5-HT and non-5-HT neurons in the RD innervate the PC and that the percentage of double-labeled cells is influenced by drug pretreatment. To determine the terminal fields of the RD efferent fibers in the PC, injections of the anterograde tracer PHA-L were also performed. Analysis of the fiber distribution in the PC further revealed some medio-lateral and antero-posterior differences.

Animals↗

PubMed1995

Automatic analysis of cortical signals recorded with voltage-sensitive dyes using a forward-backward non-linear filtering technique and deconvolution.

A method for automatically analyzing cortical signals recorded with voltage-sensitive dyes and a photodiode array is described. First, a forward-backward non-linear filtering technique is used to eliminate the background noise and preserve the fast transients of the signals. Then the filtered signals are deconvoluted from their maximal values by using a gaussian function. The different components of the signals can be identified and characterized by their respective latencies, amplitudes, plateau durations, and slopes. These parameters can be used for subsequent statistical analysis. This automated method is much faster than a manual analysis because of the large number of responses that are optically recorded. Moreover, it can be easily applied to different experimental protocols and to other signals such as field potentials.

Animals↗

PubMed1995

Projection from nucleus reuniens thalami to piriform cortex: a tracing study in the rat.

To study the cells of origin and area of termination of the projection from the nucleus reuniens thalami (NRe) to the piriform cortex (PC) we used anterograde and retrograde tracing with the B subunit of the cholera toxin. Tracer injections in the NRe resulted in anterogradely labeled fibers in the dorsolateral part of the PC layers and I and III. Following injections in the PC, retrogradely labeled cells were observed primarily in the dorsal subdivision of the NRe. Moreover, a topographical organization was observed in this subdivision: its anterior part projects to the posterior part of the PC, whereas its middle part projects to the anterior part of the PC. The present findings suggest that the NRe may exert different modulatory influences on the dorsolateral part of both anterior and posterior PC areas. The possible role of the NRe in the olfactory information processing is discussed.

Animals↗

PubMed1994

Multi-site optical recording of the rat piriform cortex activity.

Optical signals were recorded in the in vivo rat piriform cortex (PC) in response to olfactory bulb (OB) electrical stimulations delivered at 4 different sites. Afferent activity had a relatively wide (26.6% of the recorded area) but nonhomogeneous distribution on the PC surface. The different patterns of afferent activity observed in response to the 4 OB stimulations were intermixed with an overlap of only 38.5%. This activity was redistributed to the whole PC by intrinsic association fibres. The increase in the delay (from 4 ms to 12 ms) between afferent and redistributed activities along the antero-posterior axis indicated that the rostral to caudal association fibre system originating in the anterior PC was mainly responsible for the redistribution.

Animals↗

PubMed1992

Origin of the in vivo rat piriform cortex activity recorded with voltage-sensitive dyes: comparison of the optical signals and the field potentials.

The comparison of optical recordings and evoked field potentials recorded on the rat piriform cortex pointed out that both signals were strongly correlated. As the field potentials, the two waves of the optical signals originated from the mono- (direct olfactory bulb afferents) and polysynaptic (intrinsic association fibers) excitatory postsynaptic potentials. Such optical recordings will be used for studying spatiotemporal distribution of the piriform cortex activity.

Animals↗