Marianna D. Eddy

How Dogs Navigate to Catch Frisbees

Using micro-video cameras attached to the heads of 2 dogs, we examined their optical behavior while catching Frisbees. Our findings reveal that dogs use the same viewer-based navigational heuristics previously found with baseball players (i.e., maintaining the target along a linear optical trajectory, LOT, with optical speed constancy). On trials in which the Frisbee dramatically changed direction, the dog maintained an LOT with speed constancy until it apparently could no longer do so and then simply established a new LOT and optical speed until interception. This work demonstrates the use of simple control mechanisms that utilize invariant geometric properties to accomplish interceptive tasks. It confirms a common interception strategy that extends both across species and to complex target trajectories.

Electrophysiological evidence for size invariance in masked picture repetition priming

This experiment examined invariance in object representations through measuring event-related potentials (ERPs) to pictures in a masked repetition priming paradigm. Pairs of pictures were presented where the prime was either the same size or half the size of the target object and the target was either presented in a normal orientation or was a normal sized mirror reflection of the prime object. Previous masked repetition priming studies have found a cascade of priming effect sensitive to perceptual (N190/P190) and semantic (N400) properties of the stimulus. This experiment found that both early (N190/P190 effects) and later effects (N400) were invariant to size, whereas only the N190/P190 effect was invariant to mirror reflection. The combination of a small prime and a mirror reflected target led to no significant priming effects. Taken together, the results of this set of experiments suggests that object recognition, more specifically, activating an object representation, occurs in a hierarchical fashion where overlapping perceptual information between the prime and target is necessary, although not always sufficient, to activate a higher level semantic representation.

How word frequency modulates masked repetition priming: An ERP investigation

The present study used event-related potentials (ERPs) to provide precise temporal information about the modulation of masked repetition priming effectsu2009×u2009word frequency during the course of target word recognition. Contrary to the pattern seen with behavioral response times in prior research, we predicted that high-frequency words should generate larger and earlier peaking repetition priming effects than low-frequency words in the N400 time window. This prediction was supported by the results of two experiments. Furthermore, repetition priming effects in the N250 time window were found for low-frequency words in both experiments, whereas for high-frequency words these effects were seen only at the shorter (50u2009ms stimulus onset asynchrony [SOA]) used in Experiment 2, and not in Experiment 1 (70u2009ms SOA). We explain this pattern as resulting from reset mechanisms operating on the form representations activated by prime stimuli when primes and targets are processed as separate perceptual events.

The temporal dynamics of masked repetition picture priming effects: manipulations of stimulus-onset asynchrony (SOA) and prime duration

The current study used event-related potentials (ERPs) and masked repetition priming to examine the time-course of picture processing. We manipulated the stimulus-onset asynchrony (110 ms, 230 ms, 350 ms, and 470 ms) between repeated and unrepeated prime-target pairs while holding the prime duration constant (50 ms) (Experiment 1) as well as the prime durations (30 ms, 50 ms, 70 ms, and 90 ms) (Experiment 2) with a constant SOA of 110 ms in a masked repetition priming paradigm with pictures. The aim of this study was to further elucidate the mechanisms underlying previously observed ERP components in masked priming with pictures. We found that both the N/P190 and N400 are modulated by changes in prime duration and SOA, however, it appears that longer prime exposure rather than a longer SOA leads to more in-depth processing as indexed by larger N400 effects.

Masked priming and ERPs dissociate maturation of orthographic and semantic components of visual word recognition in children.

This study examined the time-course of reading single words in children and adults using masked repetition priming and the recording of event-related potentials. The N250 and N400 repetition priming effects were used to characterize form- and meaning-level processing, respectively. Children had larger amplitude N250 effects than adults for both shorter and longer duration primes. Children did not differ from adults on the N400 effect. The difference on the N250 suggests that automaticity for form processing is still maturing in children relative to adults, while the lack of differentiation on the N400 effect suggests that meaning processing is relatively mature by late childhood. The overall similarity in the childrens repetition priming effects to adults effects is in line with theories of reading acquisition, according to which children rapidly transition to an orthographic strategy for fast access to semantic information from print.

Neural Correlates of Letter Reversal in Children and Adults

Children often make letter reversal errors when first learning to read and write, even for letters whose reversed forms do not appear in normal print. However, the brain basis of such letter reversal in children learning to read is unknown. The present study compared the neuroanatomical correlates (via functional magnetic resonance imaging) and the electrophysiological correlates (via event-related potentials or ERPs) of this phenomenon in children, ages 5–12, relative to young adults. When viewing reversed letters relative to typically oriented letters, adults exhibited widespread occipital, parietal, and temporal lobe activations, including activation in the functionally localized visual word form area (VWFA) in left occipito-temporal cortex. Adults exhibited significantly greater activation than children in all of these regions; children only exhibited such activation in a limited frontal region. Similarly, on the P1 and N170 ERP components, adults exhibited significantly greater differences between typical and reversed letters than children, who failed to exhibit significant differences between typical and reversed letters. These findings indicate that adults distinguish typical and reversed letters in the early stages of specialized brain processing of print, but that children do not recognize this distinction during the early stages of processing. Specialized brain processes responsible for early stages of letter perception that distinguish between typical and reversed letters may develop slowly and remain immature even in older children who no longer produce letter reversals in their writing.

Invariance to Rotation in Depth Measured by Masked Repetition Priming is Dependent on Prime Duration

The current experiment examined invariance to pictures of objects rotated in depth using event-related potentials (ERPs) and masked repetition priming. Specifically we rotated objects 30°, 60° or 150° from their canonical view and, across two experiments, varied the prime duration (50 or 90 ms). We examined three ERP components, the P/N190, N300 and N400. In Experiment 1, only the 30° rotation condition produced repetition priming effects on the N/P190, N300 and N400. The other rotation conditions only showed repetition priming effects on the early perceptual component, the N/P190. Experiment 2 extended the prime duration to 90 ms to determine whether additional exposure to the prime may produce invariance on the N300 and N400 for the 60° and 150° rotation conditions. Repetition priming effects were found for all rotation conditions across the N/P190, N300 and N400 components. We interpret these results to suggest that whether or not view invariant priming effects are found depends partly on the extent to which representation of an object has been activated.

Development of sensitivity versus specificity for print in the visual word form area

HighlightsCompared visual word form area (VWFA) activation in children ages 7–14 vs. adults.Children showed adult‐like sensitivity to words vs. faces in VWFA.Children did not show adult‐like specificity in activation for words vs. nameable objects.Developmental specialization of VWFA extends into at least early adolescence. ABSTRACT An area near the left lateral occipito‐temporal sulcus that responds preferentially to print has been designated as the visual word form area (VWFA). Research suggests that specialization in this brain region increases as reading expertise is achieved. Here we aimed to characterize that development in terms of sensitivity (response to printed words relative to non‐linguistic faces) versus specificity (response to printed words versus line drawings of nameable objects) in typically reading children ages 7–14 versus young adults as measured by functional magnetic resonance imaging (fMRI). Relative to adults, children displayed equivalent sensitivity but reduced specificity. These findings suggest that sensitivity for print relative to non‐linguistic stimuli develops relatively early in the VWFA in the course of reading development, but that specificity for printed words in VWFA is still developing through at least age 14.

Orthographic and phonological processing in developing readers revealed by ERPs

The development of neurocognitive mechanisms in single word reading was studied in children ages 8-10 years using ERPs combined with priming manipulations aimed at dissociating orthographic and phonological processes. Transposed-letter (TL) priming (barin-BRAIN vs. bosin-BRAIN) was used to assess orthographic processing, and pseudohomophone (PH) priming (brane-BRAIN vs. brant-BRAIN) was used to assess phonological processing. Children showed TL and PH priming effects on both the N250 and N400 ERP components, and the magnitude of TL priming correlated positively with reading ability, with better readers showing larger TL priming effects. Phonological priming, on the other hand, did not correlate with reading ability. The positive correlations between TL priming and reading ability in children points to a key role for flexible sublexical orthographic representations in reading development, in line with their hypothesized role in the efficient mapping of orthographic information onto semantic information in skilled readers.