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Supplementary Material: Neuronal Responding to a Novel Cue
Figure 9. Average integrated unit neuronal activity in the nucleus accumbens, anterior and
posterior cingulate cortex, and basolateral nucleus of the amygdala in controls (top panel) and
rabbits with ventral subicular lesions (bottom panel) during extinction in the original context
with a novel CS in place of the CS+ used during conditioning. The data, in the form of z-scores
normalized with respect to a 300-ms pre-CS baseline, are shown in 40 consecutive 10-ms
intervals after the onset of the novel CS (black bars) and CS (white bars). In controls, the
cingulate cortices and basolateral nucleus of the amygdala were significantly activated by the
presence of the novel CS, manifested as an enhanced responding to the novel CS relative to the
response to the CS. This enhancement was not seen in the nucleus accumbens of controls, but
interestingly, it was found in the nucleus accumbens of rabbits with lesions of the ventral
subiculum. Responding to the novel CS was unaffected by lesions in the remaining brain areas.
These findings were supported by significant individual comparisons following the analyses of
integrated activity (see Table 1). Consistent with our data, other studies have reported that the
cingulate cortices and amygdala play a role in the detection of novel stimuli in rabbits and other
species, including rodents, primates and humans (Burns, Annett, Kelley, Everitt, & Robbins,
1996; Downar, Crawley, Mikulis, & Davis, 2001; Gabriel, Poremba, Kang, Shenker, & Maren,
unpublished manuscript; Moses, Sutherland, & McDonald, 2002; Rutishauser, Mamelak, &
Schumna, 2006; Sparenborg & Gabriel, 1990; Wilson & Rolls, 1993; Zhu, Brown, McCabe, &
Aggleton, 1995). Previous work has also suggested that the interaction of amygdalar and ventral
subicular inputs in the nucleus accumbens may control behavioral responses to novel cues
(Burns et al., 1996). Based on evidence that hippocampal inputs to the nucleus accumbens can
gate amygdalar inputs (Groenewegen, Wright, Beijer, & Voorn, 1999; Mulder, Hodenpijl, &
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Lopes da Silva, 1998), it is possible that the loss of ventral subicular inputs in rabbits with
lesions may allow amygdalar inputs to elicit more ample responses of nucleus accumbens
neurons to the novel CS.
References
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to amygdala, ventral subiculum, medial prefrontal cortex, and nucleus accumbens on the
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on the cortical response to changes in visual and auditory stimuli: An event-related fMRI
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novel stimuli during rabbits’ performance of discriminative avoidance behavior.
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Table 1
Analysis of Variance for Neuronal Activity During Extinction
Area
Term
F
df
p
Nucleus accumbens
LTS
3.16
3, 66
< 0.04
Anterior cingulate cortex
LTSI
1.56
117, 2223
< 0.054
Posterior cingulate cortex
TSI
1.74
117, 2106
< 0.04
Basolateral amygdala
TSI
2.01
117, 1872
< 0.005
Note. L = lesion (control or lesion); T= training stage (reinforced trials, original context
extinction, novel context extinction, or novel CS extinction); S = stimulus (CS+/novel CS or
CS); I = 10-ms post-CS intervals following CS onset (40 levels).
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Figure 9.