Neuroscience Letters 456 (2009) 85–88 Contents lists available at ScienceDirect Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet Retroactive interference in normal aging: A magnetoencephalography study Elena Solesio a,b,∗ , Laura Lorenzo-López c , Pablo Campo a , José María López-Frutos d , José María Ruiz-Vargas d , Fernando Maestú a,b a Centro de Magnetoencefalografía Dr. Pérez Modrego, Universidad Complutense de Madrid, Av. Complutense S/N, Pabellón 8, Medicina, Ciudad Universitaria, 28040, Madrid, Spain b Departamento de Psicología Básica II (Procesos Cognitivos), Universidad Complutense de Madrid, Campus Somosaguas S/N, 28223, Madrid, Spain c Departamento de Psicología Clínica y Psicobiología, Universidad de Santiago de Compostela, Campus Sur S/N, 15782, Santiago de Compostela, Spain d Departamento de Psicología Básica, Universidad Autónoma de Madrid, Campus Cantoblanco, 28049, Madrid, Spain article info Article history: Received 3 March 2009 Received in revised form 26 March 2009 Accepted 27 March 2009 Keywords: Aging Working memory Recognition Magnetoencephalography Interference abstract Biomagnetic responses were recorded from healthy elderly subjects (55–67 years) performing a working memory task during recognition. The objective was to identify differential spatio-temporal brain activ- ity patterns with magnetoencephalography by the presentation of two types of retroactive interference, active and passive. We obtained increased activity in the left medial temporal lobe and the left ante- rior ventral prefrontal cortex at early (100–200 ms) and medium latencies (300–400 ms) for the active interference group, and left anterior ventral prefrontal cortex showed greater activity at late latencies (700–800ms) for the passive interference group. A time-modulated ventral prefrontal activation was shown for the active and passive interference conditions indicating that executive control mechanisms were necessary in both groups. © 2009 Elsevier Ireland Ltd. All rights reserved. Contemporary memory theories enhance the prominent role of cognitive inhibition and retroactive interference in the context of working memory (WM) [11]. Cognitive inhibition is a theoretical mechanism that regulates the stopping or overriding of a mental process whereas retroactive interference is considered as an empir- ical phenomenon that results when subsequent material disrupts memory for previously learned information causing performance decrements. One of the most important issues related to inhibition and inter- ference is the role of executive control in selective retrieval: when accessing to information in the face of interference from one or more prepotent competitors, executive control ignores those non- target responses in order to carry out a successful retrieval. This is crucial to the flexible control of behaviour and suggests that inhi- bition may induce the forgetting of competing and non-desired memories [2]. The study of inhibition and interference as a plausible expla- nation for WM performance changes in normal aging has been a challenge for the last decades [8]. Indeed, behavioural studies have reported that older subjects show greater retroactive interference effects compared with young subjects [4]. In this regard, it has been ∗ Corresponding author at: Centro de Magnetoencefalografía Dr. Pérez Modrego, Universidad Complutense de Madrid, Av. Complutense S/N, Pabellón 8, Medicina, Ciudad Universitaria, 28040, Madrid, Spain. Tel.: +34 91 394 21 98; fax: +34 91 394 22 94. E-mail address: esolesio@psi.ucm.es (E. Solesio). suggested that poor performance excising interfering information occurs because of inefficient deletion mechanisms [13]. Functional neuroimaging studies of cognitive aging have found age-related deficits in WM associated to changes in the prefrontal cortex (PFC) functionality. Jonides et al. [9] demonstrated that older subjects showed less activation than young subjects in the left lateral PFC, which appears to be specifically related to resolving interference from previous information. Using functional Magnetic Resonance Imaging (fMRI), Gazza- ley et al. [6] identified age-related deficits in the suppression of cortical activity associated with task-irrelevant information, which correlated with WM impairments. Neuroimaging methods, such as fMRI, represent one of the most powerful tools with high spatial resolution. However, they fail in the description of the temporal courses of brain activity, asso- ciated with rapid physiological phenomena which are not easily modelled by many neuroimaging techniques. In this regard, mag- netoencephalography (MEG) provides excellent temporal and good spatial resolution and makes possible to examine encoding, main- tenance and retrieval memory processes individually [1]. As previously mentioned, age-related WM impairment has been attributed to deficits in inhibitory and interference control mech- anisms. Nevertheless, little is known about the impact of different interference levels on the recognition process in the elderly. The main goal of the present study was to investigate by MEG whether resistance to different levels of interference modifies brain activity in the healthy elderly. To this end, we devel- oped a delayed-match-to-sample (DMS) task descended from the 0304-3940/$ – see front matter © 2009 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2009.03.087