Verbalising visual memories

The spatiotemporal substrates of autobiographical recollection: Using event-related ICA to study cognitive networks in action

Higher cognitive functions depend upon dynamically unfolding brain network interactions. Autobiographical recollection - the autonoetic re-experiencing of context rich, emotionally laden, personally experienced episodes - is an excellent example of such a process. Autobiographical recollection unfolds over time, with different cognitive processes engaged at different times throughout. In this paper we apply a recently developed analysis technique - event related independent components analysis (eICA) - to study the spatiotemporal dynamics of neural activity supporting autobiographical recollection. Participants completed an in-scanner autobiographical recollection paradigm in which the recalled episodes varied in chronological age and emotional content. By combining eICA with these cognitive manipulations we show that the brain-wide response to autobiographical recollection comprises brain networks with (i) different sensitivities to psychological aspects of the to-be-recollected material and (ii) distinct temporal profiles of activity during recollection. We identified networks with transient activations (in language and cognitive control related regions) and deactivations (in auditory and sensorimotor regions) to each autobiographical probe question, as well as networks with responses that are sustained over the course of the recollection period. These latter networks together overlapped spatially with the broader default mode network (DMN), indicating subspecialisation within the DMN. The vividness of participants' recollection was associated with the magnitude of activation in left dorsolateral prefrontal cortex and deactivation in visual association cortices. We interpret our results in the context of current theories of the spatial and temporal organisation of the human autobiographical memory system. Our findings demonstrate the utility of eICA as a tool for studying higher cognitive functions. The application of eICA to high spatial and temporal resolution datasets identifies in a single experimental protocol spatially specific networks that are recruited during cognitive activity, as well as the temporal order of activation of these networks.

Verbal description benefits for faces when description conditions are unknown a priori

Some prior research has shown a benefit for describing nonverbal study stimuli, particularly faces, on a later recognition test relative to a control (no description) condition. In such studies, participants have known a priori whether a stimulus will need to be described, meaning that encoding differences other than the description could account for the effect. In Experiment 1, a description benefit was obtained for faces that could not be attributed to encoding differences. A direct manipulation of description duration, thus allowing more time to produce descriptors, did not influence the description effect. In Experiment 2, visual rehearsal instructions (without any verbal descriptions) failed to produce a rehearsal benefit. The experiments provide direct evidence against an account where the description or rehearsal enhances the featural information of nonverbal representations. For the present results, a benefit stemming from the encoding and retrieval of descriptors appears to be an attractive theoretical alternative over one that posits an enhancement or alteration of featural or holistic information.

A visual and semantic locus to beneficial effects of verbalization on face memory

We examined the effect of verbally describing a face on face memory as assessed in an old-new recognition task. Verbal facilitation, measured by a difference between verbalization and control conditions, was greater for upright than for inverted faces and greater for unfamiliar than for familiar faces. We propose that generating a verbal description enhances the processing of global visual information that differentiates an individual face from other faces that are encountered and also improves recognition through the association of visually derived semantic information. Verbalization enhances visual and semantic distinctiveness in memory.