Attentive and pre-attentive aspects of figural processing

Abstract

Here we use the steady-state visual evoked potential (SSVEP) to study attentive versus non-attentive processing of simple texture-defined shapes. By "tagging" the figure and background regions with different temporal frequencies, the method isolates response components associated with the figure region, the background region, and with non-linear spatio-temporal interactions between regions. Each of these response classes has a distinct scalp topography that is preserved under differing attentional task demands. In one task, attention was directed to discrimination of shape changes in the figure region. In the other task, a difficult letter discrimination was used to divert attentive processing resources away from the texture-defined form. Larger task-dependent effects were observed for figure responses and for the figure/background interaction than for the background responses. The figure region responses were delayed in occipital areas in the shape versus letter task conditions, while the region interactions were enhanced, especially in frontal areas. While a basic differentiation of figure from background processing occurred independent of task, attentive processing of elementary shapes recruited later occipital activity for figure processing and sustained non-linear figure/background interaction in frontal areas. Collectively, these results indicate that basic aspects of scene segmentation proceed pre-attentively, but that directed attention to the object shape engages a widely distributed network of brain areas including frontal and occipital regions.

Differential attentional modulation of cortical responses to S-cone and luminance stimuli

“…Although these small changes were characterized predominantly as reductions in signal lag, we note that at lower contrasts (Di or at low frequencies (Di Russo & Spinelli, 2002) the effects are similar to those we observe here. In addition, Appelbaum and Norcia (2009) recently reported a 6-ms delay in their SSVEP data caused by feature-based attention using a paradigm very similar to ours.…”

The steady-state visual evoked potential reveals neural correlates of the items encoded into visual working memory

“…Additionally, attention enhances change detection (Hollingworth, 2004; Irwin & Zelinsky, 2002; Rensink et al, 1997; Scholl, 2000; Wolfe, Reinecke, & Brawn, 2006). Moreover, many studies have demonstrated that the amplitude of visual evoked potentials and SSVEP waveforms can be modulated by attention (Anllo-Vento & Hillyard, 1996; Appelbaum & Norcia, 2009; Appelbaum, Wade, A. R., Pettet, M. W., Vildavski, V. Y., & Norcia, A. M., 2008; Hillyard et al, 1997; Mangun, 1995; Morgan et al, 1996; Müller & Hillyard, 2000). Importantly, within the VWM literature, several experiments have directly examined the influence of attention during VWM encoding (for recent reviews see (Gazzaley, 2011; Gazzaley & Nobre, 2012).…”

“…The SSVEP is an electrophysiological signal derived from the EEG in response to temporally-periodic stimuli (i.e., stimuli flickering at a specific rate). In research investigating human cognition (e.g., visual attention), the SSVEP has been most commonly considered in the frequency domain and is used specifically when analyzing signal power in the EEG at frequencies associated with the flicker rates of experimental stimuli (Appelbaum & Norcia, 2009; Hillyard et al, 1997; Morgan, Hansen, & Hillyard, 1996; Muller & Hubner, 2002; Muller et al, 1998). One simple way to 9 conceptualize the SSVEP is that a flickering stimulus will produce an EEG signal with increased power at the flicker frequency and/or one of its harmonics.…”

The time course of shape discrimination in the human brain

“…(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article. ) and not the background (Appelbaum and Norcia, 2009). As noted above, prior research indicates that neurons in both V4 and the LOC are tuned for shape attributes.…”

“…In the interest of brevity, we provide an overview of these methods, and reference the reader to our previous work (Ales and Norcia, 2009;Appelbaum and Norcia, 2009;Appelbaum et al, 2006Appelbaum et al, , 2008 for a more a more detailed description.…”