Sensory memory consolidation observed: Increased specificity of detail over days

Abstract

Memories are usually multidimensional, including contents such as sensory details, motivational state and emotional overtones. Memory contents generally change over time, most often reported as a loss in the specificity of detail. To study the temporal changes in the sensory contents of associative memory without motivational and emotional contents, we induced memory for acoustic frequency by pairing a tone with stimulation of the cholinergic nucleus basalis. Adult male rats were first tested for behavioral responses (disruption of ongoing respiration) to tones (1-15 kHz), yielding pretraining behavioral frequency generalization gradients (BFGG). They next received three days of training consisting of a conditioned stimulus (CS) tone (8.00 kHz, 70 dB, 2 s) either Paired (n = 5) or Unpaired (n = 5) with weak electrical stimulation (~48 μA) of the nucleus basalis (100 Hz, 0.2 s, co-terminating with CS offset). Testing for behavioral memory was performed by obtaining posttraining BFGGs at two intervals, 24 and 96 h after training. At 24 h post-training, the Paired group exhibited associative behavioral memory manifested by significantly larger responses to tone than the Unpaired group. However, they exhibited no specificity in memory for the frequency of the tonal CS, as indexed by a flat BFGG. In contrast, after 96 h post-training the Paired group did exhibit specificity of memory as revealed by tuned BFGGs with a peak at the CS-band of frequencies. This increased detail of memory developed due to a loss of response to lower and higher frequency sidebands, without any change in the absolute magnitude of response to CS-band frequencies. These findings indicate that the sensory contents of associative memory can be revealed to become more specific, through temporal consolidation in the absence of non-sensory factors such as motivation and emotion.

Catalpol Induces Neuroprotection and Prevents Memory Dysfunction through the Cholinergic System and BDNF

“…Previous studies reported that catalpol increased the hippocampal neuroplasticity in the aged rats [52] and attenuated MPTP-induced neuronal degeneration of nigral-striatal dopaminergic pathway in mice [53] partly attributed to BDNF upregulation. At the same time, higher BDNF level, together with ACh, is beneficial to brain plasticity and the induction of specific, associative detail behavioral memory [54, 55] and synaptogenesis [56]. In line with previous studies, our results showed that catalpol can upregulate BDNF level and here existed the strong positive correlation between the ACh level and the BDNF level in the hippocampus ( r = 0.859, P < 0.01), which are together beneficial to memory improvement and to explain from another side why catalpol ameliorated memory impairments in the SCOP-induced amnesic mice.…”

Brain Modularity in Arthropods: Individual Neurons That Support “What” But Not “Where” Memories

“…The transitory inability to display stimulus specificity could be confounded with generalization. In addition, recent experiments in mammals have shown that stimulus specificity can increase with time after training (Weinberger et al, 2009). For these reasons, in the present study the attributes of the behavioral memory were evaluated in test trials performed 24 h after training.…”

Consolidation and long-term retention of an implanted behavioral memory

“…The materials and methods were mainly identical to those previously reported (Weinberger, Miasnikov, & Chen, 2009), and will be described only briefly. All procedures were performed in accordance with the University of California Irvine Animal Research Committee and the NIH Animal Welfare guidelines.…”