[CTN] another Masami Tatsuno talk (at Laurier, Jan 23)

[Matthijs van der Meer]

Dr. Tatsuno's visit is co-sponsored by the CTN and the Psychology 
department at Laurier. He is also giving a talk there:

5:00 PM Monday, January 23, 2012, Science Bldg N2005

Title: Replay of neural activity during motor skill learning

Abstract: There is now substantial evidence showing that patterns of 
brain activity that occur during waking are replayed during subsequent 
sleep.  This replay of activity is believed to be important for memory 
consolidation, possibly driving synaptic changes that strengthen a 
memory trace.  In the declarative memory system, replay has been 
demonstrated in the areas such as hippocampus, neocortex and ventral 
striatum, the structures thought to be involved in declarative memory 
storage.  Replay in these structures has been demonstrated primarily 
during slow-wave sleep (SWS) while strong evidence for replay during REM 
sleep is lacking.  Behaviourally, rapid eye movement (REM) sleep is 
important for acquisition of non-declarative procedural memories such as 
motor skill learning.  It is not known, however, if neural activity that 
occurs during motor skill learning replays during subsequent sleep in 
general and REM sleep in particular.  To test this possibility, we used 
an array of 12 tetrodes to record ensembles of cells in rat primary 
motor cortex while the rat was trained on the single pellet reaching 
task.  Neck EMG and hippocampal EEG were also recorded to determine 
sleep/behavioural state.  We recorded 3h epochs before and after 
training on the reaching task to ensure a good sample of REM sleep.  The 
rat was naive to the reaching task and training continued for 26 d, 
until performance clearly reached asymptote.  Replay was assessed using 
explained variance (EV) which measures correlations in cell activity 
between the task and post-task sleep epochs while taking into account 
any pre-existing correlations that existed between the pre-task sleep 
and the task epochs.  Replay in the motor cortex was observed during 
both REM and SWS and occurred at multiple time points during the 3h 
post-task sleep epoch.  However, replay was confined to the first few 
days of training, during initial learning phase of the task, but not 
later during learning or when performance had reached asymptote.  This 
result agrees with evidence showing synaptic plasticity occurs 
transiently in the motor cortex during the reaching task, being observed 
during the initial learning phase, but not later when performance 
asymptotes.  Thus we have found that REM and SWS sleep contribute to 
replay of neural activity during sleep following skill learning at a 
time when synaptic plasticity is occurring.