Preserved frontal memorial processing for pictures in patients with mild cognitive impairment

Abstract

Amnestic mild cognitive impairment (aMCI) has been conceptualized as a transitional stage between healthy aging and Alzheimer's disease (AD). Therefore, understanding which aspects of memory are impaired and which remain relatively intact in these patients can be useful in determining who will ultimately go on to develop AD, and subsequently designing interventions to help patients live more engaged and independent lives. The dual-process model posits that recognition memory decisions can rely on either familiarity or recollection. Whereas research is fairly consistent in showing impaired recollection in patients with aMCI, the results have been mixed regarding familiarity. A noted difference between these studies investigating familiarity has been stimulus type. The goal of the current investigation was to use high-density event-related potentials (ERPs) to help elucidate the neural correlates of recognition decisions in patients with aMCI for words and pictures. We also hoped to help answer the question of whether patients can rely on familiarity to support successful recognition. Patients and controls participated in separate recognition memory tests of words and pictures while ERPs were recorded during retrieval. Results showed that ERP components typically associated with familiarity and retrieval monitoring were similar between groups for pictures. However, these components were diminished in the patient group for words. Based on recent work, the authors discuss the possibility that implicit conceptual priming could have contributed to the enhanced ERP correlate of familiarity. Further, the authors address the possibility that enhanced retrieval monitoring may be needed to modulate increased familiarity engendered by pictures.

Figure 1

Older adult and aMCI grand average hit and correct rejection ERP waveforms for the word condition. Each waveform represents the composite average of the seven electrodes subsuming each ROI. Components of interest are highlighted in gray: EF = early frontal effect (300-500ms), PE = parietal effect (500-800ms), LFE = late frontal effect (1000-1800ms). ROIs are listed to the left of each waveform: Left Anterior Inferior (LAI), Right Anterior Inferior (RAI), Left Anterior Superior (LAS), Right Anterior Superior (RAS), Left Posterior Superior (LPS), Right Posterior Superior (RPS), Left Posterior Inferior (LPI), and Right Posterior Inferior (RPI).

Figure 2

Older adult and aMCI grand average hit and correct rejection ERP waveforms for the picture condition. Each waveform represents the composite average of the seven electrodes subsuming each ROI. Components of interest are highlighted in gray: EF = early frontal effect (300-500ms), PE = parietal effect (500-800ms), LFE = late frontal effect (1000-1800ms). ROIs are listed to the left of each waveform: Left Anterior Inferior (LAI), Right Anterior Inferior (RAI), Left Anterior Superior (LAS), Right Anterior Superior (RAS), Left Posterior Superior (LPS), Right Posterior Superior (RPS), Left Posterior Inferior (LPI), and Right Posterior Inferior (RPI).

Figure 3

Older adult and aMCI old/new scalp topography maps for the (a) word and (b) picture conditions. Topographies are presented in 50 ms averages going forward.