The cholinergic system has been implicated in sensory cortical plasticity, learning and memory. This experiment determined the relationship between the acquisition of a Pavlovian conditioned approach response (CR) to an auditory conditioned stimulus (CS) and the release of acetylcholine (ACh) in the primary auditory cortex in rats. Samples of ACh were collected via microdialysis during behavioral training in either an auditory classical conditioning task or in a non-associative control task. The conditioning group received daily pairings of a white noise CS with a sucrose pellet unconditioned stimulus (US), while the control group received an equal number of CS and US presentations, but with these stimuli being presented randomly. Training was conducted on three consecutive days, with microdialysis samples being collected on Days 1 and 3 in separate sub-groups. The level of ACh released in the auditory cortex during conditioning trials increased from the first to the third day of training in the conditioning group as rats acquired the CR, but did not change in the control group, which did not acquire a CR. These data provide direct evidence for the hypothesis that ACh release increases in the primary auditory cortex during natural memory formation, where cholinergic activation is known to contribute to the formation of specific associative representational plasticity in conjunction with specific memory formation.
"The apparent " return " to normality of memory at 4 days for VAChT KD HET mice may simply reflect a much slower build-up of memory to regular LTM levels in the animals with decreased ACh tone, so that it would take 4 days instead of one to encode the trace. Such an explanation would be in line with recent observations of a very protracted ACh intervention in other forms of memory . Unfortunately, we were not able to see if the VAChT KD HOM mice would be able to remember the object after a longer delay (8 days) because this memory is absent even in the WT mice. "
[Show abstract][Hide abstract] ABSTRACT: Acetylcholine (ACh) is important for different cognitive functions such as learning, memory and attention. The release of ACh depends on its vesicular loading by the vesicular acetylcholine transporter (VAChT). It has been demonstrated that VAChT expression can modulate object recognition memory. However, the role of VAChT expression on object recognition memory persistence still remains to be understood. To address this question we used distinct mouse lines with reduced expression of VAChT, as well as pharmacological manipulations of the cholinergic system. We showed that reduction of cholinergic tone impairs object recognition memory measured at 24h. Surprisingly, object recognition memory, measured at 4 days after training, was impaired by substantial, but not moderate, reduction in VAChT expression. Our results suggest that levels of acetylcholine release strongly modulate object recognition memory consolidation and appear to be of particular importance for memory persistence 4 days after training.
Behavioural brain research 10/2012; 238(1). DOI:10.1016/j.bbr.2012.10.016 · 3.03 Impact Factor
"Apparently, synchronization patterns become more important for perception as task demands become more difficult either by having highly perceptually similar odors (Stopfer et al., 1997) or because more complicated processes than odor discrimination are involved, especially memorization and comparison of stimuli across time. Indeed, tasks in which a small temporal delay between stimulus and decision is involved may rely on bulbar plasticity which could be facilitated by muscarinic receptor modulation as shown in other systems (Weinberger, 2003; Roberts et al., 2005; Butt et al., 2009), however this hypothetical role of muscarinic receptors in the bulb remains to be tested. "
[Show abstract][Hide abstract] ABSTRACT: Neuromodulation in sensory perception serves important functions such as regulation of signal to noise ratio, attention, and modulation of learning and memory. Neuromodulators in specific sensory areas often have highly similar cellular, but distinct behavioral effects. To address this issue, we here review the function and role of two neuromodulators, acetylcholine (Ach) and noradrenaline (NE) for olfactory sensory processing in the adult main olfactory bulb. We first describe specific bulbar sensory computations, review cellular effects of each modulator and then address their specific roles in bulbar sensory processing. We finally put these data in a behavioral and computational perspective.
"However, recent imaging data in humans (Powers et al. 2012) suggests that these physiological integration windows may become more dynamic when tested across a range of stimulus types or when measured in behaving animals. Neuromodulators such as acetylcholine, noradrenaline, and serotonin can modulate the excitability of auditory cortical neurons (Foote et al. 1975; Hurley and Hall 2011) and are released during behavioral tasks (Stark and Scheich 1997; Butt et al. 2009). Acetylcholine release from the basal forebrain has been shown to alter the reliability of spike firing and synchrony among neurons in the visual cortex (Goard and Dan 2009), which will presumably influence the way cortical neurons multiplex sensory signals. "
[Show abstract][Hide abstract] ABSTRACT: Multisensory integration was once thought to be the domain of brain areas high in the cortical hierarchy, with early sensory cortical fields devoted to unisensory processing of inputs from their given set of sensory receptors. More recently, a wealth of evidence documenting visual and somatosensory responses in auditory cortex, even as early as the primary fields, has changed this view of cortical processing. These multisensory inputs may serve to enhance responses to sounds that are accompanied by other sensory cues, effectively making them easier to hear, but may also act more selectively to shape the receptive field properties of auditory cortical neurons to the location or identity of these events. We discuss the new, converging evidence that multiplexing of neural signals may play a key role in informatively encoding and integrating signals in auditory cortex across multiple sensory modalities. We highlight some of the many open research questions that exist about the neural mechanisms that give rise to multisensory integration in auditory cortex, which should be addressed in future experimental and theoretical studies.
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