Regular Article
Influence of Separate and Combined Septal and Amygdala Lesions on Memory, Acoustic Startle, Anxiety, and Locomotor Activity in Rats

https://doi.org/10.1006/nlme.1995.1055Get rights and content

Abstract

The septohippocampal system and the amygdala have been implicated in cognitive and emotional processes. A series of experiments was conducted to examine the effects of separate and combined lesions of these areas on a variety of behaviors, including: startle responses to acoustic stimuli; sensory gating, using prepulse inhibition of acoustic startle; anxiety, using the elevated plus-maze; locomotor activity in an open field; and memory, using both a spatial discrimination version of the Morris water maze and the inhibitory (passive) avoidance test. Both septal and fimbria-fornix lesions markedly impaired the acquisition of spatial information in the water maze, had anxiolytic-like effects in the elevated plus-maze, increased reactivity to footshock, and had marginal effects on prepulse inhibition and baseline startle. Septal and fimbria-fornix lesions also increased locomotor activity in the later stages of a session of open field exploration, but only septal lesions produced "freezing" during the early portion of this session and during inhibitory avoidance training. Amygdala lesions markedly impaired prepulse inhibition of acoustic startle. Amygdala lesions also attenuated the effects of septal lesions on freezing in the open field and on footshock reactivity, but did not affect the anxiolytic-like effects or hyperactivity associated with septal lesions. Amygdala lesions by themselves had no significant effect on water maze performance, but significantly potentiated the effects of septal lesions. These results suggest that there are dissociations between the effects of septal and fimbria-fornix lesions and that the interactions between the amygdala and septum in cognitive and emotional processes are task dependent.

References (0)

Cited by (102)

  • Acoustic startle and prepulse inhibition deficits in adult monkeys with neonatal lesions of the hippocampus, amygdala and orbital frontal cortex

    2023, Behavioural Brain Research
    Citation Excerpt :

    By contrast, the neonatal amygdala lesions had only a slight overall reduction of PPI, with no significant reduction at any specific prepulse interval. The lack of a significant reduction of PPI could relate to the small sample size used since a series of amygdala lesion or inactivation studies in rodents have shown a disruption of PPI after amygdala dysfunction in infancy or in adulthood, and most specifically after functional alteration of the basolateral nucleus of the amygdala (BLA) [10,14,31–33,70,71]. Thus, the amygdala is a critical integrative center of the limbic system, which is known to interact with many other neural substrates involved in the modulation of PPI (e.g. hippocampus, nucleus accumbens, thalamus, striatum).

  • Effect of Pleomorphic Adenoma Gene 1 Deficiency on Selected Behaviours in Adult Mice

    2021, Neuroscience
    Citation Excerpt :

    We found that KOs had significantly lower responses (%PPI) than WT, although this was only statistically significant for an ISI of 100 ms. This may suggest that Plag1 KOs have impaired sensorimotor gating. Lesions to the amygdala result in a significant reduction in PPI (Decker et al., 1995) similar to that of Plag1 KO mice, again suggesting that PLAG1 deficiency may affect amygdalar function. In addition to the amygdala, various other brain regions, such as the laterodorsal tegmental nucleus, the inferior and superior colliculi, the prefrontal cortex and the pons, are known to be involved in sensorimotor gating (Fendt et al., 2001; Swerdlow et al., 2001) and PLAG1 deficiency could affect this circuitry.

  • Psychophysical and neural correlates of noised-induced tinnitus in animals: Intra- and inter-auditory and non-auditory brain structure studies

    2016, Hearing Research
    Citation Excerpt :

    Such enhanced neurosynchrony in the AMG suggests that the limbic involvement of tinnitus is closely related to active interactions between the principal neurons in the AMG. The amygdala (AMG) is one important limbic structure that has been thought to be linked to bothersome tinnitus (Carpenter-Thompson et al., 2014; Chen et al., 2012; Jastreboff, 2004; Shulman et al., 2009; Wallhausser-Franke et al., 2006; Zhang et al., 2008, 2003b) through its role in emotional processing of anxiety, memory (Chavez et al., 2009; Sigurdsson et al., 2007) and sensorimotor gating (Decker et al., 1995). Anatomically, the AMG sends direct projections to many brain regions (Price, 2003), among which it forms circuits with auditory structures, such as the AC, to mediate auditory fear conditioning (Maren et al., 2001), learning and memory (Poremba and Gabriel, 1997), and to initiate processing of emotionally significant stimuli (Ledoux et al., 1990).

View all citing articles on Scopus
View full text