Reading relies on the rapid visual recognition of words viewed in a wide variety of fonts. We used fMRI to identify neural populations showing reduced fMRI responses to repeated words displayed in different fonts (“font-invariant” repetition suppression). We also identified neural populations showing greater fMRI responses to words repeated in a changing font as compared with words repeated in the same font (“font-sensitive” release from repetition suppression). We observed font-invariant repetition suppression in two anatomically distinct regions of the left occipitotemporal cortex (OT), a “visual word form area” in mid-fusiform cortex, and a more posterior region in the middle occipital gyrus. In contrast, bilateral shape-selective lateral occipital cortex and posterior fusiform showed considerable sensitivity to font changes during the viewing of repeated words. Although the visual word form area and the left middle occipital gyrus showed some evidence of font sensitivity, both regions showed a relatively greater degree of font invariance than font sensitivity. Our results show that the neural mechanisms in the left OT involved in font-invariant word recognition are anatomically distinct from those sensitive to font-related shape changes. We conclude that font-invariant representation of visual word form is instantiated at multiple levels by anatomically distinct neural mechanisms within the left OT.

Reading requires the neural integration of visual word form information that is split between our retinal hemifields. We examined multiple visual cortical areas involved in this process by measuring fMRI responses while observers viewed words that changed or repeated in one or both hemifields. We were specifically interested in identifying brain areas that exhibit decreased fMRI responses as a result of repeated versus changing visual word form information in each visual hemifield. Our method yielded highly significant effects of word repetition in a previously reported visual word form area (VWFA) in occipitotemporal cortex, which represents hemifield-split words as whole units. We also identified a more posterior occipital word form area (OWFA), which represents word form information in the right and left hemifields independently and is thus both functionally and anatomically distinct from the VWFA. Both the VWFA and the OWFA were left-lateralized in our study and strikingly symmetric in anatomical location relative to known face-selective visual cortical areas in the right hemisphere. Our findings are consistent with the observation that category-selective visual areas come in pairs and support the view that neural mechanisms in left visual cortex—especially those that evolved to support the visual processing of faces—are developmentally malleable and become incorporated into a left-lateralized visual word form network that supports rapid word recognition and reading.

Humans typically rely upon vision to identify object shape, but we can also recognize shape via touch (haptics). Our haptic shape recognition ability raises an intriguing question: To what extent do visual cortical shape recognition mechanisms support haptic object recognition? We addressed this question using a haptic fMRI repetition design, which allowed us to identify neuronal populations sensitive to the shape of objects that were touched but not seen. In addition to the expected shape-selective fMRI responses in dorsal frontoparietal areas, we observed widespread shape-selective responses in the ventral visual cortical pathway, including primary visual cortex. Our results indicate that shape processing via touch engages many of the same neural mechanisms as visual object recognition. The shape-specific repetition effects we observed in primary visual cortex show that visual sensory areas are engaged during the haptic exploration of object shape, even in the absence of concurrent shape-related visual input. Our results complement related findings in visually deprived individuals and highlight the fundamental role of the visual system in the processing of object shape.

We used fMRI to study figure–ground representation and its decay in primary visual cortex (V1). Human observers viewed a motion-defined figure that gradually became camouflaged by a cluttered background after it stopped moving. V1 showed positive fMRI responses corresponding to the moving figure and negative fMRI responses corresponding to the static background. This positive–negative delineation of V1 “figure” and “background” fMRI responses defined a retinotopically organized figure–ground representation that persisted after the figure stopped moving but eventually decayed. The temporal dynamics of V1 “figure” and “background” fMRI responses differed substantially. Positive “figure” responses continued to increase for several seconds after the figure stopped moving and remained elevated after the figure had disappeared. We propose that the sustained positive V1 “figure” fMRI responses reflected both persistent figure–ground representation and sustained attention to the location of the figure after its disappearance, as did subjects' reports of persistence. The decreasing “background” fMRI responses were relatively shorter-lived and less biased by spatial attention. Our results show that the transition from a vivid figure–ground percept to its disappearance corresponds to the concurrent decay of figure enhancement and background suppression in V1, both of which play a role in form-based perceptual memory.