Synaptic depression in the CA1 region of freely behaving mice is highly dependent on afferent stimulation parameters

Abstract

Persistent synaptic plasticity has been subjected to intense study in the decades since it was first described. Occurring in the form of long-term potentiation (LTP) and long-term depression (LTD), it shares many cellular and molecular properties with hippocampus-dependent forms of persistent memory. Recent reports of both LTP and LTD occurring endogenously under specific learning conditions provide further support that these forms of synaptic plasticity may comprise the cellular correlates of memory. Most studies of synaptic plasticity are performed using in vitro or in vivo preparations where patterned electrical stimulation of afferent fibers is implemented to induce changes in synaptic strength. This strategy has proven very effective in inducing LTP, even under in vivo conditions. LTD in vivo has proven more elusive: although LTD occurs endogenously under specific learning conditions in both rats and mice, its induction has not been successfully demonstrated with afferent electrical stimulation alone. In this study we screened a large spectrum of protocols that are known to induce LTD either in hippocampal slices or in the intact rat hippocampus, to clarify if LTD can be induced by sole afferent stimulation in the mouse CA1 region in vivo. Low frequency stimulation at 1, 2, 3, 5, 7, or 10 Hz given in the range of 100 through 1800 pulses produced, at best, short-term depression (STD) that lasted for up to 60 min. Varying the administration pattern of the stimuli (e.g., 900 pulses given twice at 5 min intervals), or changing the stimulation intensity did not improve the persistency of synaptic depression. LTD that lasts for at least 24 h occurs under learning conditions in mice. We conclude that a coincidence of factors, such as afferent activity together with neuromodulatory inputs, play a decisive role in the enablement of LTD under more naturalistic (e.g., learning) conditions.

Enhanced emotional responses during social coordination with a virtual partner

“…Mental disorders, like schizophrenia or autism spectrum disorder (ASD; American Psychiatric Association, 2013), which implicate socio-emotional deficits, are also associated with unstable social and/or intrapersonal motor coordination (e.g. Teitelbaum et al, 1998; Varlet et al, 2012; Fitzpatrick et al, 2013; Marsh et al, 2009, 2013). Our results are consistent with previous research and suggest that the connection between social motor coordination and emotion is an important path to understanding social emotion and the treatment of socio-emotional disorders.…”

Neurite dispersion: a new marker of multiple sclerosis spinal cord pathology?

“…Neurites were identified on the Palmgren images (4‐cluster k‐means segmentation34), and their orientation calculated with structure tensor analysis 33, 35 (spread of Gaussian kernels33: 1 μ m). Similarly to ODI, CV is an index ranging from 0 to 1, such that the variability of neurite orientations increases as CV increases.…”

mGlu5 Acts As a Switch for Opposing Forms of Synaptic Plasticity at Mossy Fiber–CA3 and Commissural Associational–CA3 Synapses

“…Exposure to novel scenes or changes of substantial aspects of these scenes facilitates input-specific LTP in synapses of the hippocampal subfields (Kemp and ManahanVaughan, 2007), including the MF-CA3 and AC-CA3 synapses (Hagena and Manahan-Vaughan, 2011). In contrast, exploration of novel spatial content enables LTD (Kemp and ManahanVaughan, 2004Goh and Manahan-Vaughan, 2013c). The CA3 region is very striking in this regard: novel exploration of landmark objects results in MF-LTD, whereas novel exploration of discrete positional features of the environment enables AC-LTD (Hagena and Manahan-Vaughan, 2011).…”