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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 drawings representing the conditioning chamber (A) and the odor box (B) used in the olfactory fear conditioning protocol. Rats were placed inside a stainless steel box located under a fume hood with lighting conditions of 420 lux (A) on day 1 (5 min) and day 2 (conditioning). A filter paper saturated with amyl acetate (5%, 250 μl) was used as the olfactory CS. Five electrical foot shocks (0.5 mA, 2 s, 40 s inter-trial interval) were used as the US. The retention of the CS-US association was tested in a Plexiglass box (B) that was also located under a fume hood with lighting conditions of 4 lux. The Plexiglass box consisted of a roof-enclosed compartment (left side) and an open (unroofed) compartment (right side). Retention was tested in 10 min sessions on the following three consecutive days (day 3, no-odor, habituation; day 4, olfactory CS exposure test; day 5, associated context, no-odor). The odor source was positioned in the opposite side of the enclosed compartment. The parameters analyzed included the percentage of time spent in the following behaviors: approaching the CS, hiding in the enclosed compartment and stretching out from the enclosed compartment toward the open compartment (head-out). The protocol was based on Dielenberg and McGregor (1999) and Kroon and Carobrez (2009).
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Figure 4: Schematic drawings representing the conditioning chamber (A) and the odor box (B) used in the olfactory fear conditioning protocol. Rats were placed inside a stainless steel box located under a fume hood with lighting conditions of 420 lux (A) on day 1 (5 min) and day 2 (conditioning). A filter paper saturated with amyl acetate (5%, 250 μl) was used as the olfactory CS. Five electrical foot shocks (0.5 mA, 2 s, 40 s inter-trial interval) were used as the US. The retention of the CS-US association was tested in a Plexiglass box (B) that was also located under a fume hood with lighting conditions of 4 lux. The Plexiglass box consisted of a roof-enclosed compartment (left side) and an open (unroofed) compartment (right side). Retention was tested in 10 min sessions on the following three consecutive days (day 3, no-odor, habituation; day 4, olfactory CS exposure test; day 5, associated context, no-odor). The odor source was positioned in the opposite side of the enclosed compartment. The parameters analyzed included the percentage of time spent in the following behaviors: approaching the CS, hiding in the enclosed compartment and stretching out from the enclosed compartment toward the open compartment (head-out). The protocol was based on Dielenberg and McGregor (1999) and Kroon and Carobrez (2009).

Mentions: Data from our laboratory have confirmed that a neutral olfactory stimulus, such as coffee odor or amyl acetate, can serve as a reliable CS in a fear conditioning paradigm (Canteras et al., 2008). As shown in Figure 4, the experimental paradigm consisted of two consecutive phases: the acquisition of olfactory fear conditioning (days 1 and 2) and the expression of olfactory fear conditioning (days 3–5). The expression of olfactory fear conditioning (second phase) was performed in an odor box (Figure 4) and consisted of three sessions: familiarization (day 3), CS-neutral odor exposure (day 4; test session), and context (day 5). During the familiarization session, the animals did not exhibit fear responses to the odor box, indicating that they did not generalize the fear response to a different context. As the animals were re-exposed to the CS-neutral odor in the odor box, they displayed clear defensive responses and spent most of the time either hiding or engaged in “head-out” behavior. They also avoided approaching the odor source. When the animals were placed in the same context without the CS-neutral odor, the animals exhibited the same sort of defensive behaviors displayed on the previous day during exposure to the CS-neutral odor. These results are important because they demonstrate that the CS-neutral odor was able to mimic a predator odor and produced clear contextually conditioned defensive behavior (Canteras et al., 2008).


Olfactory instruction for fear: neural system analysis.

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

Schematic drawings representing the conditioning chamber (A) and the odor box (B) used in the olfactory fear conditioning protocol. Rats were placed inside a stainless steel box located under a fume hood with lighting conditions of 420 lux (A) on day 1 (5 min) and day 2 (conditioning). A filter paper saturated with amyl acetate (5%, 250 μl) was used as the olfactory CS. Five electrical foot shocks (0.5 mA, 2 s, 40 s inter-trial interval) were used as the US. The retention of the CS-US association was tested in a Plexiglass box (B) that was also located under a fume hood with lighting conditions of 4 lux. The Plexiglass box consisted of a roof-enclosed compartment (left side) and an open (unroofed) compartment (right side). Retention was tested in 10 min sessions on the following three consecutive days (day 3, no-odor, habituation; day 4, olfactory CS exposure test; day 5, associated context, no-odor). The odor source was positioned in the opposite side of the enclosed compartment. The parameters analyzed included the percentage of time spent in the following behaviors: approaching the CS, hiding in the enclosed compartment and stretching out from the enclosed compartment toward the open compartment (head-out). The protocol was based on Dielenberg and McGregor (1999) and Kroon and Carobrez (2009).
© Copyright Policy
Related In: Results  -  Collection

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Figure 4: Schematic drawings representing the conditioning chamber (A) and the odor box (B) used in the olfactory fear conditioning protocol. Rats were placed inside a stainless steel box located under a fume hood with lighting conditions of 420 lux (A) on day 1 (5 min) and day 2 (conditioning). A filter paper saturated with amyl acetate (5%, 250 μl) was used as the olfactory CS. Five electrical foot shocks (0.5 mA, 2 s, 40 s inter-trial interval) were used as the US. The retention of the CS-US association was tested in a Plexiglass box (B) that was also located under a fume hood with lighting conditions of 4 lux. The Plexiglass box consisted of a roof-enclosed compartment (left side) and an open (unroofed) compartment (right side). Retention was tested in 10 min sessions on the following three consecutive days (day 3, no-odor, habituation; day 4, olfactory CS exposure test; day 5, associated context, no-odor). The odor source was positioned in the opposite side of the enclosed compartment. The parameters analyzed included the percentage of time spent in the following behaviors: approaching the CS, hiding in the enclosed compartment and stretching out from the enclosed compartment toward the open compartment (head-out). The protocol was based on Dielenberg and McGregor (1999) and Kroon and Carobrez (2009).
Mentions: Data from our laboratory have confirmed that a neutral olfactory stimulus, such as coffee odor or amyl acetate, can serve as a reliable CS in a fear conditioning paradigm (Canteras et al., 2008). As shown in Figure 4, the experimental paradigm consisted of two consecutive phases: the acquisition of olfactory fear conditioning (days 1 and 2) and the expression of olfactory fear conditioning (days 3–5). The expression of olfactory fear conditioning (second phase) was performed in an odor box (Figure 4) and consisted of three sessions: familiarization (day 3), CS-neutral odor exposure (day 4; test session), and context (day 5). During the familiarization session, the animals did not exhibit fear responses to the odor box, indicating that they did not generalize the fear response to a different context. As the animals were re-exposed to the CS-neutral odor in the odor box, they displayed clear defensive responses and spent most of the time either hiding or engaged in “head-out” behavior. They also avoided approaching the odor source. When the animals were placed in the same context without the CS-neutral odor, the animals exhibited the same sort of defensive behaviors displayed on the previous day during exposure to the CS-neutral odor. These results are important because they demonstrate that the CS-neutral odor was able to mimic a predator odor and produced clear contextually conditioned defensive behavior (Canteras et al., 2008).

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