Layla Gould

Manipulating instructions strategically affects reliance on the ventral-lexical reading stream: Converging evidence from neuroimaging and reaction time

Neurobiology of reading research has yet to explore whether reliance on the ventral-lexical stream during word reading can be enhanced by the instructed reading strategy, or whether it is impervious to such strategies. We examined Instructions: name all vs. name words (based on spelling), Word Type: regular words vs. exception words, and Word Frequency (WF) in print (log10 HAL WF) in an experiment while measuring fMRI BOLD and overt naming reaction time (RT) simultaneously. Instructions to name words increased overall reliance on the ventral-lexical stream, as measured by visible BOLD activation and the WF effect on RT, with regular words showing the greatest effects as a function of this reading strategy. Furthermore, the pattern of joint effects of these variables on RT supports the notion of cascaded, not parallel, processing. These results can be accommodated by dual-stream cascaded models of reading, and present a challenge to single-mechanism parallel processing models.

Localisation of function for noun and verb reading: Converging evidence for shared processing from fMRI activation and reaction time

Some researchers have argued in favour of verbs primarily activating the left frontal operculum (FO) in the dorsal stream, and left middle temporal (MT) region in the ventral stream, and that nouns primarily activate the left inferior temporal (IT) region in the ventral stream. Others have suggested that the activation representing noun and verb processing involves a shared neural network. We explored these hypotheses through the naming of identical, homonymous, separately cued nouns (the bat) and verbs (to bat) presented in word format using a modified naming task that ensured participants were treating the target as the appropriate part of speech (POS). Using homonymous homographs for both the noun and verb referents provides for an optimally controlled comparison given the target stimuli and responses are physically identical. Experiment 1 was a functional magnetic resonance imaging (fMRI) experiment that showed that the majority of activation was shared by both the noun and verb naming conditions, across both the ventral and dorsal streams, including the regions suggested by previous researchers as unique to verbs (FO, MT) or nouns (IT). In contrast, there was little unique activation attributable to noun processing, and practically no unique activation attributable to verb processing. This experiment, which supports a spatially shared ventral and dorsal network for noun and verb naming, was the impetus for new hypotheses involving the sharing of processes in time. Experiment 2 showed an overadditive interaction on naming reaction time (RT) between POS and bigram frequency, which provided converging evidence that the shared processing for nouns and verbs involves sublexical processing, whereas an overadditive interaction between POS and word frequency provided converging evidence that the shared processing also involves orthographic lexical access. As such, our study provides converging fMRI and RT evidence that noun and verb reading predominantly share processing along both the ventral-lexical and dorsal-sublexical reading streams.

A neuroanatomical examination of embodied cognition: semantic generation to action-related stimuli.

The theory of embodied cognition postulates that the brain represents semantic knowledge as a function of the interaction between the body and the environment. The goal of our research was to provide a neuroanatomical examination of embodied cognition using action-related pictures and words. We used functional magnetic resonance imaging (fMRI) to examine whether there were shared and/or unique regions of activation between an ecologically valid semantic generation task and a motor task in the parietal-frontocentral network (PFN), as a function of stimulus format (pictures versus words) for two stimulus types (hand and foot). Unlike other methods for neuroimaging analyses involving subtractive logic or conjoint analyses, this method first isolates shared and unique regions of activation within-participants before generating an averaged map. The results demonstrated shared activation between the semantic generation and motor tasks, which was organized somatotopically in the PFN, as well as unique activation for the semantic generation tasks in proximity to the hand or foot motor cortex. We also found unique and shared regions of activation in the PFN as a function of stimulus format (pictures versus words). These results further elucidate embodied cognition in that they show that brain regions activated during actual motor movements were also activated when an individual verbally generates action-related semantic information. Disembodied cognition theories and limitations are also discussed.

Disentangling Genuine Semantic Stroop Effects in Reading from Contingency Effects: On the Need for Two Neutral Baselines

The automaticity of reading is often explored through the Stroop effect, whereby color-naming is affected by color words. Color associates (e.g., “sky”) also produce a Stroop effect, suggesting that automatic reading occurs through to the level of semantics, even when reading sub-lexically (e.g., the pseudohomophone “skigh”). However, several previous experiments have confounded congruency with contingency learning, whereby faster responding occurs for more frequent stimuli. Contingency effects reflect a higher frequency-pairing of the word with a font color in the congruent condition than in the incongruent condition due to the limited set of congruent pairings. To determine the extent to which the Stroop effect can be attributed to contingency learning of font colors paired with lexical (word-level) and sub-lexical (phonetically decoded) letter strings, as well as assess facilitation and interference relative to contingency effects, we developed two neutral baselines: each one matched on pair-frequency for congruent and incongruent color words. In Experiments 1 and 3, color words (e.g., “blue”) and their pseudohomophones (e.g., “bloo”) produced significant facilitation and interference relative to neutral baselines, regardless of whether the onset (i.e., first phoneme) was matched to the color words. Color associates (e.g., “ocean”) and their pseudohomophones (e.g., “oshin”), however, showed no significant facilitation or interference relative to onset matched neutral baselines (Experiment 2). When onsets were unmatched, color associate words produced consistent facilitation on RT (e.g., “ocean” vs. “dozen”), but pseudohomophones (e.g., “oshin” vs. “duhzen”) failed to produce facilitation or interference. Our findings suggest that the Stroop effects for color and associated stimuli are sensitive to the type of neutral baseline used, as well as stimulus type (word vs. pseudohomophone). In general, contingency learning plays a large role when repeating congruent items more than incongruent items, but appropriate pair-frequency matched neutral baselines allow for the assessment of genuine facilitation and interference. Using such baselines, we found reading processes proceed to a semantic level for familiar words, but not pseudohomophones (i.e., phonetic decoding). Such assessment is critical for separating the effects of genuine congruency from contingency during automatic word reading in the Stroop task, and when used with color associates, isolates the semantic contribution.

The cognitive chronometric architecture of reading aloud: semantic and lexical effects on naming onset and duration.

We examined onset reaction time (RT) in a word naming task using an additive factors method (AFM). The pattern of additive and over-additive joint effects on RT among Instructions (INST: name all, name words), Word Frequency (WF: log10 HAL), Semantic Neighborhood Density (SND: Inverse Ncount), and Word Type (WT: regular, exception) supported a cognitive chronometric architecture consisting of at least two cascaded stages of processing, with the orthographic lexical system as the locus of the INST × WF and the INST × SND interactions, and the phonological output system as the locus of the WF × WT and the SND × WT interactions. Additivity between INST and WT supports the notion that these variables affect separable systems, and a WF × SND interaction supports a common locus of their effects. These results support stage-like/cascaded processing models over parallel processing models of basic reading. We also examined response duration (RD) in these data by recording and hand-marking vocal responses, which provides evidence that basic reading processes are ongoing even after the initiation of a vocal response, and supports the notion that the more lexically a word is read, the shorter the RD. As such, the effects of WT and INST on RD were opposite to their effects on RT however the effects of WF and SND on RD were in the same direction as their effects on RT. Given the combination of consistent and dissociating effects between RT and RD, these results provide new challenges to all models of basic reading processes.

Presurgical language mapping in epilepsy: Using fMRI of reading to identify functional reorganization in a patient with long-standing temporal lobe epilepsy

We report a 55-year-old, right-handed patient with intractable left temporal lobe epilepsy, who previously had a partial left temporal lobectomy. The patient could talk during seizures, suggesting that he might have language dominance in the right hemisphere. Presurgical fMRI localization of language processing including reading of exception and regular words, pseudohomophones, and dual meaning words confirmed the clinical hypothesis of right language dominance, with only small amounts of activation near the planned surgical resection and, thus, minimal eloquent cortex to avoid during surgery. Postoperatively, the patient was rendered seizure-free without speech deficits.

Inclusion of attentional networks in the pre-surgical neuroimaging assessment of a large deep hemispheric cavernous malformation: an FMRI case report.

Background and Importance: Functional magnetic resonance imaging (fMRI) is a noninvasive and reliable tool for mapping eloquent cortex in patients prior to brain surgery. Ensuring intact perceptual and cognitive processing is a key goal for neurosurgeons, and recent research has indicated the value of including attentional network processing in pre-surgical fMRI in order to help preserve such abilities, including reading, after surgery. Clinical Presentation: We report a 42-year-old patient with a large cavernous malformation, near the left basal ganglia. The lesion measured 3.8 × 1.7 × 1.8 cm. In consultation with the patient and the multidisciplinary cerebrovascular team, the decision was made to offer the patient surgical resection. The surgical resection involved planned access via the left superior parietal lobule using stereotactic location. The patient declined an awake craniotomy; therefore, direct electrocortical stimulation (ECS) could not be used for intraoperative language localization in this case. Pre-surgical planning included fMRI localization of language, motor, sensory, and attentional processing. The key finding was that both reading and attention-processing tasks revealed consistent activation of the left superior parietal lobule, part of the attentional control network, and the site of the planned surgical access. Given this information, surgical access was adjusted to avoid interference with the attentional control network. The lesion was removed via the left inferior parietal lobule. The patient had no new neurologic deficits postoperatively but did develop mild neuropathic pain in the left hand. Conclusion: This case report supports recent research that indicates the value of including fMRI maps of attentional tasks along with traditional language-processing tasks in preoperative planning in patients undergoing neurosurgery procedures.

The beat goes on: the effect of rhythm on reading aloud

ABSTRACT The central aim of this experiment was to explore the connection between rhythm and reading processes by examining whether reading aloud is affected by the presentation of a rhythmic prime that was either congruent or incongruent with the syllabic stress of the target letter string. The targets were words that placed the stress on either the first or second syllable (practice vs. police), as well as their corresponding pseudohomophones (PHs) (praktis vs. poleese). The results demonstrated that naming reaction times were faster for PHs when the rhythmic prime was congruent with the syllabic stress, and slower when the rhythmic prime was incongruent. These results are taken to suggest that PHs showed a larger effect given that they must be phonetically decoded. The congruency by stimulus type interaction suggests that their effects reflect at least one common stage of processing, namely grapheme to phoneme translation. In general, these results indicate that a rhythmic prime matched to the syllabic stress of a letter string that requires phonetic decoding aids sublexical reading processes, which has important implications for allowing models of reading to account for rhythm processes. The current paradigm may also reveal potential remedial applications for treating speech deficits in patient populations, such as Parkinsons disease, stuttering, aphasia, and dyslexia.

Examining the neuroanatomical and the behavioural basis of the effect of basic rhythm on reading aloud

ABSTRACT We used functional magnetic resonance imaging (fMRI) to examine the brain regions associated with the effect of congruency between rhythmic stress and syllabic stress on reading aloud (Gould et al., 2016). The region of particular interest was the putamen, which has been shown to be involved in speech processing, rhythm processing, and predicting upcoming events. The task involved naming words that placed the stress on either the first or second syllable (practice versus police), as well as their corresponding pseudohomophones (praktis versus poleese) that were preceded by either a congruent or incongruent rhythmic prime. The fMRI results revealed that a network involving the putamen is involved, and the behavioural results demonstrated that a rhythmic prime matched to the syllabic stress aids reading processes of both words and PHs. Implications for neurobiological models of reading, as well as clinical applications (e.g. speech rehabilitation in Parkinson’s disease) are discussed.

More than a feeling: The bidirectional convergence of semantic visual object and somatosensory processing

Prevalent theories of semantic processing assert that the sensorimotor system plays a functional role in the semantic processing of manipulable objects. While motor execution has been shown to impact object processing, involvement of the somatosensory system has remained relatively unexplored. Therefore, we developed two novel priming paradigms. In Experiment 1, participants received a vibratory hand prime (on half the trials) prior to viewing a picture of either an object interacted primarily with the hand (e.g., a cup) or the foot (e.g., a soccer ball) and reported how they would interact with it. In Experiment 2, the same objects became the prime and participants were required to identify whether the vibratory stimulation occurred to their hand or foot. In both experiments, somatosensory priming effects arose for the hand objects, while foot objects showed no priming benefits. These results suggest that object semantic knowledge bidirectionally converges with the somatosensory system.