False memory for spatial location is mediated by V1
Jessica M. Karanian1,2, Scott D. Slotnick3; 1Wesleyan University, 2Tufts University, 3Boston College
Prior fMRI results have given rise to the view that true memories, but not false memories, activate early sensory cortex. It is thought that false memories, which reflect conscious processing, do not activate early sensory cortex because these regions are associated with nonconscious processing. We posited that false memories may activate early sensory cortex when task conditions are manipulated to evoke conscious processing. In an fMRI experiment, during encoding, abstract shapes were presented to the left or right of fixation. During retrieval, old shapes were presented at fixation and participants characterized each as previously on the “left” or “right” followed by a “unsure”–“sure”–“very sure” confidence rating. False memories for spatial location (i.e., “right”/left or “left”/right + “very sure” or “sure”) were associated with activity in bilateral early visual regions, including V1. In a follow-up fMRI-guided TMS experiment, we assessed whether V1 activity was necessary for false memory construction by temporarily disrupting processing in this region. The identical memory paradigm was employed and, between the encoding and retrieval phases of each run, TMS (1 Hz, 8 min) was employed to target the location of false memory activity (identified in the fMRI experiment) in left V1, right V1, or the vertex (a control site). False memories for spatial location were significantly reduced following TMS to V1, as compared to vertex (χ2 (1) = 8.06, p < .01). The results of the present experiments provide strong evidence that early sensory cortex can contribute to false memory construction under particular task conditions.
Topic Area: LONG-TERM MEMORY: Episodic