Brief, prior, exposure to red decreases categorical and coordinate spatial task performance
Introduction
The brain processes visuospatial information through at least two types of spatial relation representations. One type, categorical spatial relations, indicates where an object is relative to another object, without regard to the metric distance between the two objects. Often, categorical spatial information consists of cardinal-based relations, represented by descriptors such as “above/below” or “to the left/right” of a reference object. For example, when looking at a clock face, one can note the relative position of the number 12 as being located above the number 6. The second type, coordinate spatial relations, indicates metric distance without regard to relative location (Kosslyn, 1987). In the same example of looking at a clock face, coordinate discrimination can include judgment of the exact position of where the center of the clock is.
One pathway involved in vision results in stimulus information being first processed at the retina, and then traveling through the optic nerve and subsequently through the lateral geniculate nucleus (LGN) to reach the striate cortex. Subsequent processing occurs through the ventral and dorsal streams (i.e. the “what” and “where” pathways, respectively) in order to understand what an object is and where an object is located. The “what” stream follows a pathway to the inferior temporal lobe and the “where” stream follows a pathway to the parietal lobe. It has been hypothesized that categorical and coordinate discriminations are associated with “where” pathway function in the brain (Kosslyn, 1987).
Evidence suggests that two separate pathways process categorical and coordinate information (Baumann et al., 2012, Hellige, 1996, Kosslyn et al., 1992, Roth and Hellige, 1998). Kosslyn et al. (1992) carried out a set of neural-network computer simulations, which indicated that input filtered through large, overlapping receptive fields were more efficient in computing coordinate spatial information. They also found that input filtered through small, non-overlapping receptive fields were more efficient in computing categorical spatial information. Adding to this point, the left hemisphere has been shown to be more efficient in processing information containing small attended areas (corresponding to Kosslyn’s network for categorical information), whereas the right hemisphere has been shown to be more effective at processing information containing large attended areas (corresponding to Kosslyn’s network for coordinate information; Ivry and Robertson, 1998, Laeng et al., 2004). This has been corroborated by the results of Roth and Hellige (1998), where there was a left visual field advantage (inferring more efficient right hemisphere activity) for coordinate spatial processing, and a right visual field advantage (inferring more efficient left hemisphere activity) for categorical spatial processing. Finally, in an fMRI study examining brain activation during the encoding of coordinate and categorical information, Baumann et al. (2012) found greater activation in the parietal cortex during encoding of categorical information, and greater activation in the medial temporal cortex and in the dorsal striatum during encoding of coordinate information. Thus demonstrating that different areas of the brain were activated during categorical vs. coordinate tasks.
Given that the magnocellular visual system is comprised of cells with large, overlapping receptive fields and the parvocellular system is comprised of cells with small, non-overlapping receptive fields, and based on Kosslyn’s findings mentioned above, coordinate processing is theorized to be reliant on magnocellular function, and categorical processing is theorized to be reliant on parvocellular function (Kosslyn, Chabris, Marsolek, & Koenig, 1992). The magnocellular visual system is one component of the LGN, and it produces rapid and brief responses that are sensitive to low spatial frequencies, low contrast, and high temporal resolution. The magnocellular visual system is involved with processing information related to motion, location of visual stimuli, and brightness discrimination. The parvocellular visual system is the second component of the LGN, and it produces slower and longer responses that are sensitive to high spatial frequencies, however this system demonstrates low contrast sensitivity. This system is involved in processing visual stimuli detail and color (Derrington and Lennie, 1984, Kaplan and Shapley, 1982). Although these two visual systems are often described as functioning independently of one another, evidence from a neural inactivation study suggests that the two systems communicate with each other (Ferrera, Nealey, & Maunsell, 1992). Additionally, Kosslyn et al. (1992) suggested that the magnocellular pathway is more efficient processing via the right hemisphere over the left hemisphere, and the opposite for the parvocellular pathway, with more efficient processing via the left hemisphere over the right hemisphere (Laeng et al., 2004).
The magnocellular pathway is comprised of type III and type IV neural cells. Type IV cells are characterized by their large receptive fields, which function through center surround mechanisms. These cells have a surround that is sensitive to red light, such that when it is presented, it leads to inhibition of neural firing (Livingstone & Hubel, 1984). As mentioned earlier, the magnocellular pathway is involved with coordinate spatial processing, thus red light should decrease coordinate spatial abilities, which can impact general spatial processing abilities. Several studies reported decreased general spatial performance on tasks that either feature red target stimuli or targets on red backgrounds (Breitmeyer and Breier, 1994, Hellige and Cumberland, 2001, Maehara et al., 2004, Roth and Hellige, 1998, Seno et al., 2010). For example, Breitmeyer and Breier (1994) found increased reaction times to detect large diameter spot stimuli when presented on red backgrounds compared to blue or green backgrounds. Additionally, Seno et al. (2010) found that perception of vection was weaker when dots were presented on a red background compared to a green background.
There have also been studies examining the inhibitory behavioral effects of the color red on categorical and coordinate processing. In Roth and Hellige (1998), and in a subsequent replication study (Hellige & Cumberland, 2001), participants were asked to indicate if a line would be able to fit between two dots in the coordinate task. In this task, a judgment of metric distance is required to make an accurate decision, and information about relative position is superfluous, because all lines were between the two dots. They found that reaction time was slower with a red background compared to a green background for these coordinate task trials. In the categorical task, participants were asked to indicate whether dots were above or below a line. In this task, a judgment on relative position is required to make a correct decision, however information about the metric distance from the dots to the line is irrelevant to making a correct decision. The results of the categorical task trials show that there was a non-significant trend towards slower reaction times with a green background compared to a red background. This indicates that coordinate processing, but not categorical processing, is affected by the inhibitory effects of red light, likely the result of the magnocellular system’s response to red.
An additional factor to consider when examining the effects of red presentation on the magnocellular system is the timing of the neural response. Results from primate electrophysiological studies show that there is a period of time that elapses before a magnocellular response can occur following stimulus presentation. One study found that magnocellular cells, on average, demonstrated a response latency of approximately 37 ms from the onset of an achromatic visual stimulus (Levitt, Schumer, Sherman, Spear, & Movshon, 2001). This means that a neural response in the magnocellular LGN occurs approximately 37 ms after the stimulus was presented. It is possible then, that a stimulus presented briefly will have impact on magnocellular firing after the offset of the stimulus. The present study examined this possibility by presenting brief flashes of color prior to the presentation of the target stimulus, which is a Gabor patch.
The previously mentioned studies (Roth and Hellige, 1998, Hellige and Cumberland, 2001) demonstrated the effects of red light during the presentation of target stimuli. However, given that there is a delay in magnocellular responding to visual stimuli, we sought to examine the effects of red stimuli on magnocellular pathway function prior to the presentation of the target stimulus. In addition we sought to examine this phenomenon in a more ecologically valid task than that which was used in Roth and Hellige, 1998, Hellige and Cumberland, 2001 as described in the methods below. Given that magnocellular processing is related to coordinate processing, we expected to observe decreases in spatial task performance in coordinate trials with a red prime relative to green or grey color primes, if prior exposure to red has an inhibitory effect on magnocellular processing. Given that a relationship between categorical processing and magnocellular system function has not been supported by the literature (see Hellige and Cumberland, 2001, Roth and Hellige, 1998) we do not expect to observe decreases in categorical task performance with a red prime relative to green or grey color primes.
From a theoretical perspective, this research will provide additional information regarding the effects of color on spatial processing. In addition, if there is a decrease in coordinate spatial performance following presentation of the color red, there are practical implications. For example, findings may be important to daily activities that require spatial navigation in the presence of red visual stimuli, such as encountering red lights or stop signs when driving. If prior presentation of red decreases coordinate spatial perception abilities, it is possible that driving performance could be impacted. In addition, the results can have clinical relevance; when assessing visuospatial abilities through neuropsychological testing, prior presentation of red colored test stimuli could have the potential to decrease spatial performance on subsequent test items.
Section snippets
Participants
98 consistent-right-handers (Mage = 19.40, SDage = 1.73; 21 male, 77 female) completed the study for SONA credit in their Psychology course. Participants were considered to be consistent-right-handed (CRH) if they scored an +85 or above on the Edinburgh Handedness Inventory (EHI) (Christman, 2014). Handedness was restricted to consistent right-handed participants to reduce potential effects of cortical organization variability, thereby reducing the likelihood of finding effects of the
Participants
A total of 90 consistent right handers (Mage = 19.91, SDage = 2.65; 14 male, 75 female, 1 other) completed the study for course SONA credit compensation. Participants were excluded from the study if they exhibited color vision deficits on the Ishihara test. All procedures were approved by the Institutional Review Board at Montclair State University, and conducted in conformance with the Declaration of Helsinki
Materials
All materials in Experiment 2 were the same as in Experiment 1, except for the
General discussion
Prior studies have shown that presentation of either red target stimuli or target stimuli on red backgrounds leads to decreased accuracy and/or increased reaction time (Breitmeyer and Breier, 1994, Hellige and Cumberland, 2001, Maehara et al., 2004, Roth and Hellige, 1998, Seno et al., 2010). The proposed mechanism is through inhibition of magnocellular pathway function, and this is related to coordinate spatial task performance. The results from both Experiment 1 and Experiment 2 confirm that
CRediT authorship contribution statement
Sophia Lall: Investigation, Formal analysis, Data curation, Writing - original draft, Visualization. Tad T. Brunye: Conceptualization, Methodology, Software. Melissa Barua: Investigation. Ruth E. Propper: Conceptualization, Methodology, Resources, Writing - review & editing, Supervision, Project administration.
Acknowledgements
The authors thank Melissa Villafana for assistance in data collection.
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