Neglect is a multifactorial syndrome typically ascribed to an attentional disorder in detecting and identifying stimuli in the contralesional body or space. The concept of attention is central not only to cognitive theories but also to understand the behavioral consequences of brain damage in neuropsychological analysis and theorizing. For example, whether visuospatial neglect – commonly exhibited by patients with right-brain damage – should be considered a perceptual or attentional phenomenon has been debated since the early 20th century. Over time, an attentional interpretation has gained the upper hand, while sensory/perceptual limitations have been progressively pushed aside. Rosenholtz’s article presents new insights into re-evaluating impairments in visual search, as seen in neglect patients.

The current evidence on visuospatial neglect aligns with the (prevailing) attentional interpretation of the disorder in explaining contralateral omissions in several tasks. However, some phenomena related to neglect remain challenging to address theoretically. One such example is “allocentric” or “object-centered” neglect (Behrmann & Moscovitch, Reference Behrmann and Moscovitch1994; Olson, Reference Olson2003). In tasks such as drawing, copying, or searching for a target among multiple stimuli, patients with right-brain damage may omit the left portion of objects regardless of their location in the visual field (e.g., Gainotti, Messerli, & Tissot, Reference Gainotti, Messerli and Tissot1972). This response profile contrasts with the classical egocentric form of neglect, where patients fail to search for stimuli contralateral to their lesion.

Some case reports, particularly those concerning neglect dyslexia, suggest that these patients may experience higher-level attentional disorders (Driver & Halligan, Reference Driver and Halligan1991; Hillis & Caramazza, Reference Hillis and Caramazza1991; Miceli & Capasso, Reference Miceli and Capasso2001). However, other studies show error types (i.e., letter substitutions on the left part of words) aligned with what is predicted by a perceptual integration deficit (Martelli, Arduino, & Daini, Reference Martelli, Arduino and Daini2011; Daini et al., Reference Daini, Albonico, Malaspina, Martelli, Primativo and Arduino2013). Still, a comprehensive theoretical framework for understanding allocentric neglect remains elusive. Conversely, it has been proposed that spatial representations invariably depend on egocentric reference frames (Filimon, Reference Filimon2015). Therefore, drawing on Rosenholtz’s proposal, an interpretation arises: that perceptual limitations characteristic of peripheral vision might provide a more straightforward explanation for the behavioral pattern.

Tests of allocentric neglect can be conducted using various tasks (Lee et al., Reference Lee, Lim, Jeong, Kim and Jang2022). The complexity of the target may influence performance, with more complex targets being more susceptible to the spatial arrangement of stimuli (Gainotti & Ciaraffa, Reference Gainotti and Ciaraffa2013). Stimulus complexity impairs peripheral object recognition in brain-damaged patients (Strappini et al., Reference Strappini, Pelli, Di Pace and Martelli2017). Many clinical assessments use visual search tasks, where patients scan several small targets that can be identified with just one or a few eye fixations. In the Apples test (Bickerton et al., Reference Bickerton, Samson, Williamson and Humphreys2011) or the Broken Hearts test (Demeyere et al., Reference Demeyere, Riddoch, Slavkova, Bickerton and Humphreys2015), allocentric neglect is indicated by the inability to detect gaps on the left side of visual stimuli. However, it is reasonable to suggest that performance could be jointly influenced by the observer’s fixation pattern across multiple targets and the peripheral limitations within each fixation. Both could, in principle, indicate a perceptual or an attentional defect.

From Rosenholtz’s perspective, allocentric neglect may be an interesting phenomenon for contrasting interpretations based on attention versus perceptual limitations associated with peripheral vision. Notably, many neglect patients exhibit various forms of visual field defects. Some may experience extinction to double visual stimuli (with contralesional stimuli omitted when a similar stimulus is simultaneously presented in the ipsilesional visual field side). Extra-personal neglect can be double dissociated from hemianopia and extinction (Pavlovskaya, Soroker, & Bonneh, Reference Pavlovskaya, Soroker and Bonneh2007). However, group studies indicate a considerable overlap among these conditions, such as that several neglect patients have field defects (Doricchi et al., Reference Doricchi, Guariglia, Figliozzi, Silvetti, Bruno and Gasparini2005) or visual extinction (Vossel et al., Reference Vossel, Eschenbeck, Weiss, Weidner, Saliger, Karbe and Fink2011).

Assessing visual field defects and extinction in neglect patients is inherently challenging, as it can be difficult to determine whether omissions on the left side arise from a visual field defect, extinction, or exploratory difficulties (e.g., Müller-Oehring et al., Reference Müller-Oehring, Kasten, Poggel, Schulte, Strasburger and Sabel2003). Regarding visual field defects, various behavioral measures exhibit different sensitivities, with the standard confrontation procedure being the least sensitive (De Luca et al., Reference De Luca, Zeri, Matano, Di Lorenzo, Ciurli, Mulas and Nardo2024). Alternatively, evoked potentials (e.g., Keyser, Neetens, & Vissenberg, Reference Keyser, Neetens and Vissenberg1991) may yield conflicting results compared to behavioral measures (Watanabe et al., Reference Watanabe, Shinoda, Kimura, Mashima, Oguchi and Ohde2007). In large-scale studies, data on visual field defects are either absent (Marsh & Hillis, Reference Marsh and Hillis2008) or limited to simple assessments (Bickerton et al., Reference Bickerton, Samson, Williamson and Humphreys2011; Demeyere & Gillebert, Reference Demeyere and Gillebert2019). Similar considerations apply to extinction measurements. Simple confrontation tests can be challenging with neglect patients, and more sensitive methods have been confined to a limited number of focused studies. When methods sensitive to detecting extinction in neglect patients are used, several patients with extra-personal neglect also exhibit visual extinction (Vossel et al., Reference Vossel, Eschenbeck, Weiss, Weidner, Saliger, Karbe and Fink2011). Overall, neglect can be reliably dissociated from peripheral disturbances, such as visual field defects and visual extinction. However, in unselected groups of right-brain-damaged patients, several neglect patients show various forms of visual field defect or visual extinction, these patients being critical for Rosenholtz’s conjecture.

Can deficits in visual processing contribute to what is described as object-based or allocentric neglect? In scanning tasks, the stimuli are relatively small, and each likely requires an eye fixation for proper processing (i.e., to avoid crossing out stimuli with a missing part on the left). Information from the left of the fixation point is crucial for carrying out such tasks. If visual input is degraded, as in the case of extinction, or absent, as in hemianopia, patients may fail to detect the missing part on the left and complete the stimulus gestaltically. Bickerton et al. (Reference Bickerton, Samson, Williamson and Humphreys2011) considered this possibility, noting that several (although not all) patients with neglect and hemianopia exhibited an allocentric profile when assessed using the Apples test.

Overall, the perspective proposed by Rosenholtz presents a fresh and intriguing approach to the study of neglect. Traditionally, research has centered on identifying double dissociations, which have advanced our understanding of how various brain lesions can create processing asymmetries in perceiving the external world. However, recognizing the presence of dissociations does not negate that, in most patients, observable behavior is influenced by a combination of co-existing symptoms. In this vein, some studies have revealed diverse response profiles in patients with neglect, depending on the co-presence and type of field defects (Doricchi et al., Reference Doricchi, Guariglia, Figliozzi, Magnotti and Gabriele2003, Reference Doricchi, Guariglia, Figliozzi, Silvetti, Bruno and Gasparini2005). While extra-personal neglect can be double dissociated from deficits such as hemianopia or extinction, the interplay between early or mid-level vision and exploratory deficits may have been overlooked in understanding allocentric forms of neglect. The theoretical framework proposed by Rosenholtz may open an interesting avenue for research in this area.