title: Basal forebrain activation controls contrast sensitivity in primary visual cortex.
abstract: BACKGROUND
  The basal forebrain (BF) regulates cortical activity by the action of cholinergic projections to the cortex. At the same time, it also sends substantial GABAergic projections to both cortex and thalamus, whose functional role has received far less attention. We used deep brain stimulation (DBS) in the BF, which is thought to activate both types of projections, to investigate the impact of BF activation on V1 neural activity.
  
  
  RESULTS
  BF stimulation robustly increased V1 single and multi-unit activity, led to moderate decreases in orientation selectivity and a remarkable increase in contrast sensitivity as demonstrated by a reduced semi-saturation contrast. The spontaneous V1 local field potential often exhibited spectral peaks centered at 40 and 70 Hz as well as reliably showed a broad γ-band (30-90 Hz) increase following BF stimulation, whereas effects in a low frequency band (1-10 Hz) were less consistent. The broad γ-band, rather than low frequency activity or spectral peaks was the best predictor of both the firing rate increase and contrast sensitivity increase of V1 unit activity.
  
  
  CONCLUSIONS
  We conclude that BF activation has a strong influence on contrast sensitivity in V1. We suggest that, in addition to cholinergic modulation, the BF GABAergic projections play a crucial role in the impact of BF DBS on cortical activity.
authors.affiliation: Department of Medicine, University of Fribourg, Chemin du Musée 5, Fribourg 1700, Switzerland.
authors.forename: Anwesha
authors.initials: A
authors.lastname: Bhattacharyya
authors.forename: Julia
authors.initials: J
authors.lastname: Veit
authors.forename: Robert
authors.initials: R
authors.lastname: Kretz
authors.forename: Igor
authors.initials: I
authors.lastname: Bondar
authors.forename: Gregor
authors.initials: G
authors.lastname: Rainer
mesh_terms: D000818:Animals; D001931:Brain Mapping; D015350:Contrast Sensitivity / Q000502:physiology*; D004558:Electric Stimulation; D005074:Evoked Potentials, Visual / Q000502:physiology*; D009949:Orientation / Q000502:physiology; D010775:Photic Stimulation; D016548:Prosencephalon / Q000502:physiology*; D013057:Spectrum Analysis; D014418:Tupaiidae; D014793:Visual Cortex / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology