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Olfactory instruction for fear: neural system analysis.

Canteras NS, Pavesi E, Carobrez AP - Front Neurosci (2015)

Bottom Line: Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses.Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor.In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo São Paulo, Brazil.

ABSTRACT
Different types of predator odors engage elements of the hypothalamic predator-responsive circuit, which has been largely investigated in studies using cat odor exposure. Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses. Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor. In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning. In the second section, we reviewed how chemical stimulation of the PMd and PAGdl may serve as a useful unconditioned stimulus in an olfactory fear conditioning paradigm; these experiments provide an interesting perspective for the understanding of learned fear to predator odor. Finally, in the third section, we explored the fact that neutral odors that acquire an aversive valence in a shock-paired conditioning paradigm may mimic predator odor and mobilize elements of the hypothalamic predator-responsive circuit.

No MeSH data available.


Related in: MedlinePlus

Schematic diagram showing the putative circuit involved in the expression of olfactory fear conditioning to a neutral odor that was previously paired with footshock (shown in black lines) as well as the PMd–AMv path and the cortical-hippocampal-amygdalar circuit that are putatively involved in second-order contextual conditioning (shown in red lines). ACA, anterior cingulate area; AHN, anterior hypothalamic nucleus; AMv, anteromedial thalamic nucleus, ventral part; BMAp, basomedial amygdalar nucleus, posterior part; ECT, ectorhinal area; HF, hippocampal formation; LA, lateral amygdalar nucleus; LS, lateral septum; PAG, periaqueductal gray; PERI, perirhinal area; PL, prelimbic area; PMd, dorsal premammillary nucleus; RSP, retrosplenial area; VMHdm, ventromedial hypothalamic nucleus, dorsomedial part. See text for discussion.
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Figure 6: Schematic diagram showing the putative circuit involved in the expression of olfactory fear conditioning to a neutral odor that was previously paired with footshock (shown in black lines) as well as the PMd–AMv path and the cortical-hippocampal-amygdalar circuit that are putatively involved in second-order contextual conditioning (shown in red lines). ACA, anterior cingulate area; AHN, anterior hypothalamic nucleus; AMv, anteromedial thalamic nucleus, ventral part; BMAp, basomedial amygdalar nucleus, posterior part; ECT, ectorhinal area; HF, hippocampal formation; LA, lateral amygdalar nucleus; LS, lateral septum; PAG, periaqueductal gray; PERI, perirhinal area; PL, prelimbic area; PMd, dorsal premammillary nucleus; RSP, retrosplenial area; VMHdm, ventromedial hypothalamic nucleus, dorsomedial part. See text for discussion.

Mentions: As shown in Figure 6, associative learning between conditioned and unconditioned stimuli is likely to occur in the lateral amygdalar nucleus. In support of this view, tetrodotoxin infusion in the region of the lateral amygdalar nucleus has been shown to impair the acquisition of olfactory fear conditioning (Kilpatrick and Cahill, 2003). Notably, the lateral amygdalar nucleus may influence the medial hypothalamic predator-responsive circuit through its dense projections to the posterior part of the basomedial amygdalar nucleus, which provides substantial input to the ventromedial hypothalamic nucleus (Petrovich et al., 1996). Alternatively, as pointed by Cádiz-Moretti et al. (2014), information about pain stimuli (relayed through the posterior intralaminar thalamic complex and the parabrachial area) and neutral odors (relayed through indirect projections from the piriform cortex and cortical amygdala) may converge in the MEApv, a critical site for responses to predator odors, and this association at the MEApv could easily explain how a neutral odor that was previously paired with foot shock would engage elements of the predator-responsive hypothalamic circuit. However, further studies are needed to provide support for this hypothesis.


Olfactory instruction for fear: neural system analysis.

Canteras NS, Pavesi E, Carobrez AP - Front Neurosci (2015)

Schematic diagram showing the putative circuit involved in the expression of olfactory fear conditioning to a neutral odor that was previously paired with footshock (shown in black lines) as well as the PMd–AMv path and the cortical-hippocampal-amygdalar circuit that are putatively involved in second-order contextual conditioning (shown in red lines). ACA, anterior cingulate area; AHN, anterior hypothalamic nucleus; AMv, anteromedial thalamic nucleus, ventral part; BMAp, basomedial amygdalar nucleus, posterior part; ECT, ectorhinal area; HF, hippocampal formation; LA, lateral amygdalar nucleus; LS, lateral septum; PAG, periaqueductal gray; PERI, perirhinal area; PL, prelimbic area; PMd, dorsal premammillary nucleus; RSP, retrosplenial area; VMHdm, ventromedial hypothalamic nucleus, dorsomedial part. See text for discussion.
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Figure 6: Schematic diagram showing the putative circuit involved in the expression of olfactory fear conditioning to a neutral odor that was previously paired with footshock (shown in black lines) as well as the PMd–AMv path and the cortical-hippocampal-amygdalar circuit that are putatively involved in second-order contextual conditioning (shown in red lines). ACA, anterior cingulate area; AHN, anterior hypothalamic nucleus; AMv, anteromedial thalamic nucleus, ventral part; BMAp, basomedial amygdalar nucleus, posterior part; ECT, ectorhinal area; HF, hippocampal formation; LA, lateral amygdalar nucleus; LS, lateral septum; PAG, periaqueductal gray; PERI, perirhinal area; PL, prelimbic area; PMd, dorsal premammillary nucleus; RSP, retrosplenial area; VMHdm, ventromedial hypothalamic nucleus, dorsomedial part. See text for discussion.
Mentions: As shown in Figure 6, associative learning between conditioned and unconditioned stimuli is likely to occur in the lateral amygdalar nucleus. In support of this view, tetrodotoxin infusion in the region of the lateral amygdalar nucleus has been shown to impair the acquisition of olfactory fear conditioning (Kilpatrick and Cahill, 2003). Notably, the lateral amygdalar nucleus may influence the medial hypothalamic predator-responsive circuit through its dense projections to the posterior part of the basomedial amygdalar nucleus, which provides substantial input to the ventromedial hypothalamic nucleus (Petrovich et al., 1996). Alternatively, as pointed by Cádiz-Moretti et al. (2014), information about pain stimuli (relayed through the posterior intralaminar thalamic complex and the parabrachial area) and neutral odors (relayed through indirect projections from the piriform cortex and cortical amygdala) may converge in the MEApv, a critical site for responses to predator odors, and this association at the MEApv could easily explain how a neutral odor that was previously paired with foot shock would engage elements of the predator-responsive hypothalamic circuit. However, further studies are needed to provide support for this hypothesis.

Bottom Line: Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses.Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor.In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo São Paulo, Brazil.

ABSTRACT
Different types of predator odors engage elements of the hypothalamic predator-responsive circuit, which has been largely investigated in studies using cat odor exposure. Studies using cat odor have led to detailed mapping of the neural sites involved in innate and contextual fear responses. Here, we reviewed three lines of work examining the dynamics of the neural systems that organize innate and learned fear responses to cat odor. In the first section, we explored the neural systems involved in innate fear responses and in the acquisition and expression of fear conditioning to cat odor, with a particular emphasis on the role of the dorsal premammillary nucleus (PMd) and the dorsolateral periaqueductal gray (PAGdl), which are key sites that influence innate fear and contextual conditioning. In the second section, we reviewed how chemical stimulation of the PMd and PAGdl may serve as a useful unconditioned stimulus in an olfactory fear conditioning paradigm; these experiments provide an interesting perspective for the understanding of learned fear to predator odor. Finally, in the third section, we explored the fact that neutral odors that acquire an aversive valence in a shock-paired conditioning paradigm may mimic predator odor and mobilize elements of the hypothalamic predator-responsive circuit.

No MeSH data available.


Related in: MedlinePlus