Memory Encoding Task (Static and Scrambled)

PI Name: Jerzy Szaflarski, MD

Email: szaflaj@ucmail.uc.edu

Areas: ??????

Program: PsyScope 1.1 on Mac G3 and Direct RT

Durations: 7 min and 15 sec

Special Equipment: Visual Presentation System, Hand Button Press

Description: The activation task was a scene encoding paradigm, using a balanced mixture of color indoor or outdoor scenes (including abstract scenes) that could be encoded verbally or nonverbally; some scenes included people/faces (50% of the pictures were indoor and 50% outdoor scenes). This choice of stimuli has the advantage of combining items that can be encoded either verbally or nonverbally into one paradigm to avoid performing evaluations with multiple fMRI tasks. This activation paradigm is based on studies showing that the encoding of novel pictures significantly increases fMRI signal in both hippocampi. During the stimuli presentation, participants were instructed to memorize all scenes for further memory testing. There were seven blocks of 10 pictures (70 pictures). During the scene encoding, participants were exposed to scene pictures for 2.5 seconds followed by 0.5 second of a white blank screen. During the control condition, participants viewed pairs of scrambled images alternating with white/blank screen using the same luminosity and timing parameters as the encoding task and made a judgment whether the scrambled pictures were the same or different (50% of image pairs were the same). This control condition allowed us to subtract away the visual-perceptual and decision-making aspects of the encoding tasks when the two tasks were directly compared, better isolating the memory encoding component of the scene encoding task. Attention to the task was monitored by asking the participants to respond to the pictures by indicating whether this is an indoor or outdoor scene, or whether the scrambled pictures are the same or different. Participants made responses by pushing appropriate buttons on a button box held in the right hand, and all responses were recorded for further analysis. The total duration of the entire paradigm was 7 minutes 15 seconds (including 15 seconds of a control condition followed by seven 30-second periods of encoding interleaved with seven 30-second periods of the control condition). The stimuli were presented using PsyScope 1.1 running on an Apple Macintosh G3 computer. Before data collection, the participants familiarized themselves with the scanner to decrease possible anxiety related to the scanning procedure. Foam padding and a head restraint were used to control head movement. Participants used push buttons to give responses and, if necessary, to alert the MRI technologist to a problem. Their understanding of the memory task was tested by performing a mock run that included 5 indoor/outdoor scenes and 5 scrambled picture pairs. Participants were allowed to proceed to the scanner only if they responded correctly to all 10 items. Within 10 minutes of completing the MRI scanning, participants were tested on their recognition of the images presented during the encoding task. Sixty indoor/outdoor scenes were presented with balanced content of target and foil pictures; each picture was presented for 6 seconds to give the participants ample time for reviewing the pictures and providing responses. Participants were asked to indicate whether they remembered seeing any of the pictures while undergoing fMRI procedure by pushing "Y" or "N" buttons on standard computer keyboard. The responses were stored for further analysis.