title: Post-Stroke Longitudinal Alterations of Inter-Hemispheric Correlation and Hemispheric Dominance in Mouse Pre-Motor Cortex.
abstract: OBJECTIVE
  Limited restoration of function is known to occur spontaneously after an ischemic injury to the primary motor cortex. Evidence suggests that Pre-Motor Areas (PMAs) may "take over" control of the disrupted functions. However, little is known about functional reorganizations in PMAs. Forelimb movements in mice can be driven by two cortical regions, Caudal and Rostral Forelimb Areas (CFA and RFA), generally accepted as primary motor and pre-motor cortex, respectively. Here, we examined longitudinal changes in functional coupling between the two RFAs following unilateral photothrombotic stroke in CFA (mm from Bregma: +0.5 anterior, +1.25 lateral).
  
  
  METHODS
  Local field potentials (LFPs) were recorded from the RFAs of both hemispheres in freely moving injured and naïve mice. Neural signals were acquired at 9, 16 and 23 days after surgery (sub-acute period in stroke animals) through one bipolar electrode per hemisphere placed in the center of RFA, with a ground screw over the occipital bone. LFPs were pre-processed through an efficient method of artifact removal and analysed through: spectral,cross-correlation, mutual information and Granger causality analysis.
  
  
  RESULTS
  Spectral analysis demonstrated an early decrease (day 9) in the alpha band power in both the RFAs. In the late sub-acute period (days 16 and 23), inter-hemispheric functional coupling was reduced in ischemic animals, as shown by a decrease in the cross-correlation and mutual information measures. Within the gamma and delta bands, correlation measures were already reduced at day 9. Granger analysis, used as a measure of the symmetry of the inter-hemispheric causal connectivity, showed a less balanced activity in the two RFAs after stroke, with more frequent oscillations of hemispheric dominance.
  
  
  CONCLUSIONS
  These results indicate robust electrophysiological changes in PMAs after stroke. Specifically, we found alterations in transcallosal connectivity, with reduced inter-hemispheric functional coupling and a fluctuating dominance pattern. These reorganizations may underlie vicariation of lost functions following stroke.
authors.affiliation: Institute of Biophysics, CNR, Pisa, Italy.|Translational Neural Engineering Area, The Biorobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Vallone
authors.affiliation: Translational Neural Engineering Area, The Biorobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Lai
authors.affiliation: Neuroscience Institute, CNR, Pisa, Italy.|Life Science Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Spalletti
authors.affiliation: Translational Neural Engineering Area, The Biorobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Panarese
authors.affiliation: Scuola Normale Superiore, Pisa, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Alia
authors.affiliation: Translational Neural Engineering Area, The Biorobotics Institute, Scuola Superiore Sant'Anna, Pisa, Italy.|Bertarelli Foundation Chair in Translational Neuroengineering Center for Neuroprosthetics and Institute of Bioengineering School of Engineering Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland.
authors.forename: Silvestro
authors.initials: S
authors.lastname: Micera
authors.affiliation: Neuroscience Institute, CNR, Pisa, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Caleo
authors.affiliation: Institute of Biophysics, CNR, Pisa, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Di Garbo
mesh_terms: D000465:Algorithms; D000818:Animals; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods; D004195:Disease Models, Animal; D004566:Electrodes; D019054:Evoked Potentials, Motor; D005552:Forelimb; D007839:Functional Laterality / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D015233:Models, Statistical; D009044:Motor Cortex / Q000293:injuries* / Q000503:physiopathology*; D009991:Oscillometry; D020127:Recovery of Function / Q000502:physiology; D020521:Stroke / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D013927:Thrombosis; D013997:Time Factors