Role of oscillations in visual perception: attention and working memory

Julkaisun otsikon käännös: Oskillaatioiden rooli näköhavainnossa: tarkkaavaisuus ja työmuisti

Santeri Rouhinen

Tutkimustuotos: OpinnäyteVäitöskirjaArtikkelikokoelma

Abstrakti

People have large differences in their visual attentional and working memory (WM) abilities. Both attention and WM are thought to comprise of representation of sensory information and its attentional / executive control. A common finding is that people’s ability to attend to or to memorize several items concurrently ranges from 2 to 4 items. How attention and working memory functions arise from distributed brain activity and what mechanisms limit the attentional and working memory capacity are largely unknown.

In this thesis, concurrent magnetoencephalography and electroencephalography (MEG and EEG) recordings of whole brain activity combined with source modeling were used to study the role of rhythmic cortical activity in attention and WM. Visual attention was studied with a multiple object tracking task (MOT), where the subjects tracked 1–4 moving target objects with and without distracter objects. The functional role local oscillations amplitudes as well as the significance of large-scale inter-areal synchronization in setting the capacity of visual attention were studied. We found a decrease in oscillation amplitudes at relatively lower frequencies (alpha–beta), and an increase at higher frequencies in the gamma band (30–90 Hz) as a function of attentional load. The load-dependent oscillation amplitude modulations differed in better and worse performing subjects (i.e. subjects with high and low attentional capacity, respectively). In high-capacity subjects, gamma amplitudes increased more strongly as a function of load in widespread cortical regions including lateral PFC, temporal and visual areas, whereas in the low capacity subjects load dependent gamma amplitude increase was smaller. Large-scale inter-areal synchronization was found at low theta (4–5 Hz) and high-gamma (70–90 Hz) bands. The most robust connections were observed between the left and right PFCs and between visual areas and PFC. The load-dependent strengthening in inter-areal synchronization differed between high and low capacity subjects at several frequencies. These results suggest that both local and inter-areal rhythmic activity differences can explain differences in attentional capacity.

Visual working memory was studied with a delayed match-to-sample WM task, where different visual features or their conjunctions were retained in WM. The functional role of load-dependent oscillation amplitudes in remembering different features were studied. Distinct load-dependent differences in local gamma-band amplitudes were found to reflect maintenance of specific visual features in WM. Gamma band oscillations were also increased for the memorizing the conjunction of features supporting their role in binding of visual features. These results suggest that especially rhythmic gamma activity is important in maintaining visual information WM.

Taken together our results suggest common mechanisms for visual attention and VWM, and that gamma oscillations work in a highly task specific manner, and that gamma oscillations are critical for perception.
Julkaisun otsikon käännösOskillaatioiden rooli näköhavainnossa: tarkkaavaisuus ja työmuisti
Alkuperäiskielienglanti
Myöntävä instituutio
Valvoja/neuvonantaja
  • Palva, Satu, Valvoja
  • Palva, Matias, Valvoja
Myöntöpäivämäärä4 jouluk. 2018
JulkaisupaikkaHelsinki
Kustantaja
Painoksen ISBN978-951-51-4634-2
Sähköinen ISBN978-951-51-4635-9
TilaJulkaistu - 14 marrask. 2018
OKM-julkaisutyyppiG5 Tohtorinväitöskirja (artikkeli)

Tieteenalat

  • 1184 Genetiikka, kehitysbiologia, fysiologia
  • Neurotiede
  • 6162 Kognitiotiede
  • Systeemitaso

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