The Visual Spatial Attention Controversy

For decades, there has been a controversy on whether visual spatial attention modulates activity in V1 and extrastriate cortex, which includes V2, V3, and V4. Proponents of the majority view initially thought that activity in V1 was not modulated by attention. They claimed that the attentional modulation in V1 could occur late in time via feedback from extrastriate cortex. The supporters of the minority view “have provided evidence that V1 attention effects can occur rapidly which, if true, would indicate that this region is of central importance during this cognitive process” (Slotnick). In class, we discussed eight studies that had mixed views. 

For example, Di Russo et al. (2003), Heize et al. (1994), Ding et al. (2014), and Baumgartner et al. (2018) are all major proponents of the majority view. Di Russo et al. (2003) claimed that the V1 area is not “modulated by spatial attention and that the earliest attentional influences are upon visual processing in extrastriate areas starting at 70 to 80 (milliseconds) ms.” Although this study argues that there were no significant effects of attention on the amplitudes of either the C1 or P2 components, there was a slightly larger response in C1 for the waveforms of the attended (thick line) compared to the unattended (thin line) ERPs, which could be significant. Heize et al. (1994) used ERP recordings in humans and showed that attended visual stimuli are preferentially selected as early as 80-90 ms after stimulus onset. However, their ERP methods did not give a precise localization of the activated cortical areas.When they combined PET and ERP recordings, neither measurement showed that spatial attention influenced processing in the striate cortex. Furthermore, the researchers predict that the modulation in the ventral extrastriate visual cortex, contralateral to the direction of attention, could be unrelated to alertness.

Ding et al. (2014) examined the effects of high versus low attentional load on the C1 components elicited by both task-relevant and irrelevant stimuli. Although Figure 5 shows an early difference seen in the C1 waveform, further measurements showed “no significant load effect on the C1 amplitude for either UVF or LVF, as revealed by paired t-tests on the mean amplitude of C1 (80-100 ms) comparing low-load and high-load conditions at the midline parieto-occipital sites” (p. 3011). In other words, this study is a proponent of the majority view since the earliest visual evoked C1 component did not show a significant load modulation for either the peripheral task-irrelevant stimuli or the central task-relevant stimuli. Baumgartner et al. (2018) used the same analysis strategies as Kelly et al. (2008) and found no evidence for an attention-based modulation of the C1 (measured from 50-80 ms). For example, Figure 6 shows that the evoked C1 topography is distinct from the evoked P1 topography, and there were modulations only during the early and late phases of the P1. There were no significant modulations observed during the C1 time window (50-80 ms).  

Kelly et al. (2008), Sajedin et al. (2019), Motter (1993), and Dassanayake et al. (2016) are proponents of the minority view. Kelly et al. (2008) found a spatial attentional modulation of the C1 component of the human ERP as quickly 57 ms. For example, Figure 3A shows the “ERP responses averaged over all 11 subjects, contrasting the conditions of attention toward and away from each location…The ANOVA testing the C1 component revealed a significant main effect of attention” (p. 2632). Since C1 primarily reflects activity in the V1 region, this finding is important because it contradicts the theory that V1 activity is impenetrable during the initial afference. Furthermore, Sajedin et al. (2019) claim that ACh enhances the amplitude of evoked sensory responses and performs a filtering role through enhancing relevant inputs while suppressing weak sensory inputs. This leads to sharpening of the neurons in the sensory cortex. For example, Figure 5C shows that “applying ACh to 15% of the inhibitory interneurons in the population sharpened the orientation tuning width by 15.3% for high ACh level condition and 8% for low ACh level.”  Motter (1993) argues that directed focal attention “does result in changes in the response of some V1, V2, and V4 neurons to otherwise identical stimuli at spatially specific locations” (p. 915). For example, in both V1 and V2 areas, 70% of the neurons had greater responses when focal attention was directed toward the receptive-field location.  However, only 58% of the neurons in the area V4 showed a greater response to the stimulus when attention was directed to the receptive field (Figure 5). Furthermore, Dassanayake et al. (2016) concluded that “exogenous visual attention can facilitate the earliest stage of cortical processing under HTP conditions” (p. 9). For instance, table 5 showed no significant validity effect on C1 mean latency in any of the sites at any of the SOA conditions. 

Taking all these articles together,  I cannot ignore the significant findings of the Motter (1993) and Kelly et al. (2008) and I am siding with the proponents of the minority view. I would propose a study on undergraduate students and stimulate their right parietal cortex which would lead to a temporary left visual field neglect. Then, I would measure the modulations in the V1 and extrastriate cortex before and after the application of TMS. Since brain lesions can lead to the problem of voluntary attentional control, I would use exogenous cueing. My hypothesis would be that I would see a major effect of the parietal lobe lesion on the C1 component. A followup experiment would be to study the modulation of attention on the A1 component in the auditory cortex and compare it to the C1 component in the visual cortex.


Baumgartner, H. M., Graulty, C. J., Hillyard, S. A., & Pitts, M. A. (2017). Does spatial attention modulate the earliest component of the visual evoked potential? Cognitive Neuroscience, 9(1-2), 4–19. doi: 10.1080/17588928.2017.1333490

Dassanayake, T. L., Michie, P. T., & Fulham, R. (2016). Effect of temporal predictability on exogenous attentional modulation of feedforward processing in the striate cortex. International Journal of Psychophysiology, 105, 9–16. doi: 10.1016/j.ijpsycho.2016.04.007

Ding, Y., Martinez, A., Qu, Z., & Hillyard, S. A. (2013). Earliest stages of visual cortical processing are not modified by attentional load. Human Brain Mapping, 35(7), 3008–3024. doi: 10.1002/hbm.22381

Heinze, H. J., Mangun, G. R., Burchert, W., Hinrichs, H., Scholz, M., Münte, T. F., … Hillyard, S. A. (1994). Combined spatial and temporal imaging of brain activity during visual selective attention in humans. Nature, 372(6506), 543–546. doi: 10.1038/372543a0

Kelly, S. P., Gomez-Ramirez, M., & Foxe, J. J. (2008). Spatial Attention Modulates Initial Afferent Activity in Human Primary Visual Cortex. Cerebral Cortex, 18(11), 2629–2636. doi: 10.1093/cercor/bhn022

Motter, B. C. (1993). Focal attention produces spatially selective processing in visual cortical areas V1, V2, and V4 in the presence of competing stimuli. Journal of Neurophysiology, 70(3), 909–919. doi: 10.1152/jn.1993.70.3.909

Russo, F. D., Martinez, A., & Hillyard, S. A. (2003). Source Analysis of Event-related Cortical Activity during Visuo-spatial Attention. Cerebral Cortex, 13(5), 486–499. doi: 10.1093/cercor/13.5.486

Sajedin, A., Menhaj, M. B., Vahabie, A.-H., Panzeri, S., & Esteky, H. (2019). Cholinergic Modulation Promotes Attentional Modulation in Primary Visual Cortex- A Modeling Study. Scientific Reports, 9(1). doi: 10.1038/s41598-019-56608-3

Slotnick, S. (2013). Controversies in Cognitive Neuroscience. doi: 10.1007/978-1-137-27236-2

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