Revisiting the unlimited capacity and pre-attentive view of iconic memory: cognitive and neurophysiologic estudies

MARTÍN GRAZIANO; ARIEL ZYLBERBERG; MARIANO SIGMAN

Huerta Grande, Córdoba (Argentina)

Congreso; IRCN First Joint Meeting of the Argentine Society for Neurosciences (SAN) and the Argentine Workshop in Neurosciences (TAN); 2009

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; mso-hyphenate:none; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES; mso-fareast-language:AR-SA;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Crowded stimuli are initially stored in a high-capacity sensory buffer which decays exponentially in hundred of milliseconds. Only a fraction of this buffer – referred as iconic memory - access higher cognitive states such as working memory or consciousness. Previous studies have omited the question of how this sensory buffer interacts with the ongoing dynamic state of the brain. The aim of this work is to analyze the interaction of ongoing cognitive or attentional processes with the sensory representations in iconic memory, and to revisit its pre-attentional conceptualization. We hypothesize that these factors modulate and influence the initial sensory representation of the stimuli, thus limiting the capacity of this memory and consequently the later access of the items to working memory or consciousness. We used a partial report paradigm where subjects had to report the identity of a letter presented in a cued position of a circle array around a fixation point, where the delay between stimulus and cue was systematically varied. We provide evidence of the limited capacity of iconic memory using different numbers of items in the array. We suggest that this limited capacity arise from a limited distribution of attentional resources (with a finite capacity) and we provide examples of different dynamics across spatial positions. A simple mathematical model assuming a limited buffer capacity explains this memory saturation effect. Finally, we present an EEG study to analyze the interaction between attention and iconic memory.