Search

Abnormalities in the simplest form of learning, habituation, have been reported in a variety of neuropsychiatric disorders as etiologically diverse as Autism Spectrum Disorder, Fragile X syndrome, Schizophrenia, Parkinson’s Disease, Huntington’s Disease, Attention Deficit Hyperactivity Disorder, Tourette’s Syndrome, and Migraine. Here we provide the first comprehensive review of what is known about alterations in this form of non-associative learning in each disorder. Across several disorders, abnormal habituation is predictive of symptom severity, highlighting the clinical significance of habituation and its importance to normal cognitive function. Abnormal habituation is discussed within the greater framework of learning theory and how it may relate to disease phenotype either as a cause, symptom, or therapy. Important considerations for the design and interpretation of habituation experiments are outlined with the hope that these will aid both clinicians and basic researchers investigating how this simple form of learning is altered in disease. [ABSTRACT FROM AUTHOR]

Learning is critical for survival as it provides the capacity to adapt to a changing environment. At the molecular and cellular level, learning leads to alterations within neural circuits that include synaptic rewiring and synaptic plasticity. These changes are mediated by signalling molecules known as neuromodulators. One such class of neuromodulators are neuropeptides, a diverse group of short peptides that primarily act through G protein-coupled receptors. There has been substantial progress in recent years on dissecting the role of neuropeptides in learning circuits using compact yet powerful invertebrate model systems. We will focus on insights gained using the nematode Caenorhabditis elegans, with its unparalleled genetic tractability, compact nervous system of ∼300 neurons, high level of conservation with mammalian systems and amenability to a suite of behavioural analyses. Specifically, we will summarise recent discoveries in C. elegans on the role of neuropeptides in non-associative and associative learning. [ABSTRACT FROM AUTHOR]

Abstract: The ability to learn and remember is critical for all animals to survive in the ever-changing environment. As we age, many of our biological faculties decay and of these, decline in learning and memory can be the most distressing. To carefully define age-dependent changes in learning during reproductive age in the nematode Caenorhabditis elegans, we performed a parametric behavioral study of habituation to nonlocalized mechanical stimuli (petri plate taps) over a range of intensities in middle-aged worms. We found that as worms age (from the onset of reproduction to the end of egg laying), response probability habituation increases (at both 10- and 60-second interstimulus intervals) and that these age-related changes were associated with a decrease in the discrimination between stimuli of different intensities. We also used optogenetics to investigate where these age-dependent changes occur. Our data suggest that the changes occur upstream of mechanosensory neuron depolarization. These data support the idea that declines in stimulus intensity discrimination abilities during aging may be one variable underlying age-related cognitive deficits. [Copyright &y& Elsevier]