Evelyn C. Ferstl

The Anterior Frontomedian Cortex and Evaluative Judgment: An fMRI Study

This study investigated the neuronal basis of evaluative judgment. Judgments can be defined as the assessment of an external or internal stimulus on an internal scale and they are fundamental for decision-making and other cognitive processes. Evaluative judgments (I like George W. Bush: yes/no) are a special type of judgment, in which the internal scale is related to the persons value system (preferences, norms, aesthetic values, etc.). We used functional magnetic resonance imaging to examine brain activation during the performance of evaluative judgments as opposed to episodic and semantic memory retrieval. Evaluative judgment produced significant activation in the anterior frontomedian cortex (BA 10/9), the inferior precuneus (BA 23/31), and the left inferior prefrontal cortex (BA 45/47). The results show a functional dissociation between the activations in the anterior frontomedian cortex and in the inferior precuneus. The latter was mainly activated by episodic retrieval processes, supporting its function as a multimodal association area that integrates the different aspects of retrieved and newly presented information. In contrast, the anterior frontomedian cortex was mainly involved in evaluative judgments, supporting its role in self-referential processes and in the self-initiation of cognitive processes.

The extended language network: A meta-analysis of neuroimaging studies on text comprehension

Language processing in context requires more than merely comprehending words and sentences. Important subprocesses are inferences for bridging successive utterances, the use of background knowledge and discourse context, and pragmatic interpretations. The functional neuroanatomy of these text comprehension processes has only recently been investigated. Although there is evidence for right‐hemisphere contributions, reviews have implicated the left lateral prefrontal cortex, left temporal regions beyond Wernickes area, and the left dorso‐medial prefrontal cortex (dmPFC) for text comprehension. To objectively confirm this extended language network and to evaluate the respective contribution of right hemisphere regions, meta‐analyses of 23 neuroimaging studies are reported here. The analyses used replicator dynamics based on activation likelihood estimates. Independent of the baseline, the anterior temporal lobes (aTL) were active bilaterally. In addition, processing of coherent compared with incoherent text engaged the dmPFC and the posterior cingulate cortex. Right hemisphere activations were seen most notably in the analysis of contrasts testing specific subprocesses, such as metaphor comprehension. These results suggest task dependent contributions for the lateral PFC and the right hemisphere. Most importantly, they confirm the role of the aTL and the fronto‐medial cortex for language processing in context. Hum Brain Mapp 2008.

The role of coherence and cohesion in text comprehension: an event-related fMRI study

Text processing requires inferences for establishing coherence between successive sentences. In neuropsychological studies and brain imaging studies, these coherence-building processes have been ascribed to the right hemisphere. On the other hand, there is evidence for prefrontal brain damage causing non-aphasic language disorders, in which text level processes are impaired. In this study, we used an event-related, whole-head fMRI methodology to evaluate the contributions of prefrontal areas and the right hemisphere to coherence building. We scanned 12 participants while they read 120 sentence pairs and judged their coherence. Four conditions were used, resulting from crossing coherence and cohesion (i.e. the presence of a lexical connection). A behavioral pretest confirmed that cohesion aided establishing coherence, whereas it hindered the detection of coherence breaks. In the fMRI study, all language conditions yielded activation in left frontolateral and temporolateral regions, when compared to a physical control task. The differences due to coherence of the sentence pairs were most evident in larger activation for coherent as compared to incoherent sentence pairs in the left frontomedian wall, but also in posterior cingulate and precuneal regions. Finally, a left inferior prefrontal area was sensitive to the difficulty of the task, and in particular to the increase in processing costs when cohesion falsely indicated coherence. These results could not provide evidence for a special involvement of the right hemisphere during inferencing. Rather, they suggest that the left frontomedian cortex plays an important role in coherence building.

Emotional and Temporal Aspects of Situation Model Processing during Text Comprehension: An Event-Related fMRI Study

Language comprehension in everyday life requires the continuous integration of prior discourse context and general world knowledge with the current utterance or sentence. In the neurolinguistic literature, these so-called situation model building processes have been ascribed to the prefrontal cortex or to the right hemisphere. In this study, we use whole-head event-related fMRI to directly map the neural correlates of narrative comprehension in context. While being scanned using a spin-echo sequence, 20 participants listened to 32 short stories, half of which contained globally inconsistent information. The inconsistencies concerned either temporal or chronological information or the emotional status of the protagonist. Hearing an inconsistent word elicited activation in the right anterior temporal lobe. The comparison of different information aspects revealed activation in the left precuneus and a bilateral frontoparietal network for chronological information. Emotional information elicited activation in the ventromedial prefrontal cortex and the extended amygdaloid complex. In addition, the integration of inconsistent emotional information engaged the dorsal frontomedial cortex (Brodmanns area 8/9), whereas the integration of inconsistent temporal information required the lateral prefrontal cortex bilaterally. These results indicate that listening to stories can elicit activation reflecting content-specific processes. Furthermore, updating of the situation model is not a unitary process but it also depends on the particular requirements of the text. The right hemisphere contributes to language processing in context, but equally important are the left medial and bilateral prefrontal cortices.

Functional specialization within the anterior medial prefrontal cortex: a functional magnetic resonance imaging study with human subjects

This study investigated the functional neuroanatomy of the anterior medial prefrontal cortex (aMPFC). Previous studies have shown that the aMPFC is involved in evaluative judgment and self-referential processes. Specifically, different sections of the aMPFC are differentially influenced by attention demanding processes. Whereas the dorsal section is supposed to be involved in self-referential processes, the ventral section is assumed to be attenuated during attention demanding processes. The present study investigates the involvement of the dorsal and ventral aMPFC in evaluative judgment by using functional magnetic resonance imaging with spin-echo echo-planar-imaging. Processes involved in evaluative judgment are attention-demanding, self-referential and activate regions in the dorsal and ventral section of the aMPFC. Attention demanding tasks do not necessarily lead to an attenuation of the ventral section of the aMPFC, a region mainly involved in emotional and affective processing.

Text comprehension after brain injury: left prefrontal lesions affect inference processes.

Comprehending language in context requires inferencing, particularly for the establishment of local coherence. In the neurolinguistic literature, an inference deficit after right hemisphere brain damage has been postulated, but clinical observation and imaging data suggest that left-frontal lesions might also result in inference deficits. In the present experiment, 25 nonaphasic patients performed a coherence judgment task requiring them to indicate a pragmatic connection between 2 successively presented sentences. Patients with left-temporal or right-frontal lesions performed the task well. In contrast, patients with left- and bifrontal lesions exhibited the most severe deficit. Both error rates and response times were elevated for coherent trials as compared with incoherent trials. These results confirm that the left-frontal lobe contributes to inference processes.

Making sense of nonsense: An fMRI study of task induced inference processes during discourse comprehension

Inferences during discourse comprehension are needed to connect subsequent sentences to each other. Previous studies have implicated the dorso-medial prefrontal cortex (dmPFC) as important for successful coherence building. The present study addressed the question of whether the dmPFC activation could be modulated by the task instructions or whether it was a function of stimulus properties. In a graded coherence judgment task, participants rated on a 4-point scale the closeness of the pragmatic connection between subsequent sentences. 75% of the sentence pairs had previously been identified as incoherent, so that some creativity was needed for finding a pragmatic connection. Of particular interest were the incoherent sentence pairs rated as somewhat related, because this novel condition allowed to separate stimulus properties from the inference success. Compared to the unrelated sentence pairs, this condition elicited increased activation in fronto-parietal regions related to executive functions, reflecting the difficulty of the search for coherence. Compared to coherent sentence pairs, activations in the bilateral fusiform gyri were found. This suggests a role for visual and spatial situation model building during inferencing. Most importantly, the time course of the signal change in the fronto-medial cortex confirmed that all rating conditions engaged this brain region to an equal degree, and that the process extended throughout the relatively long decision period. These results confirm that the dmPFC activation can be modulated by task instructions and that it reflects non-automatic cognitive processes, subserving the integration between external stimulation and idiosyncratic response criteria.

Assessment of story comprehension deficits after brain damage

A story comprehension task was specifically developed for the clinical diagnosis of text comprehension deficits. The performance of 49 healthy control participants on qualitatively different Yes/No questions confirmed that both salience and explicitness of information had an impact on question difficulty. An unselected group of brain damaged patients (n=96) made more errors, particularly on questions about implicit information. The subgroup of patients with left-hemispheric vascular aetiology (n=18) had particular difficulties with stated details, patients with right-hemispheric vascular aetiology (n=12) with implicit main ideas, and patients with traumatic brain injury (n=34) were most impaired on implicit information. Correlations with neuropsychological test scores also confirmed that the questions successfully tapped different subprocesses of comprehension. Performance on implicit main ideas was correlated with tests of executive functions, whereas the performance on the other three question types was correlated with long-term memory and verbal learning. These results suggest that the story comprehension test is a useful diagnostic tool for neuropsychological assessment.

Time, space and emotion: fMRI reveals content-specific activation during text comprehension

Story comprehension involves building a situation model of the text, i.e., a representation containing information on the who, where, when and why of the story. Using fMRI at 3T, domain-specific activations for three different information aspects were sought. Twenty participants read two sentence stories half of which contained inconsistencies concerning emotional, temporal or spatial information. Partly replicating previous results [E.C. Ferstl, M. Rinck, D.Y. von Cramon, Emotional and temporal aspects of situation model processing during text comprehension: an event-related fMRI study, J. Cogn. Neurosci. 17 (2005) 724-739], the anterior lateral prefrontal cortex/orbito-frontal cortex proved important for processing temporal information. The left anterior temporal lobe was particularly important during emotional stories. Most importantly, spatial information elicited bilateral activation in the collateral sulci and the posterior cingulate cortex, areas important for visuo-spatial cognition. These findings provide further evidence for content-specific processes during text comprehension.

Emotional valence and arousal affect reading in an interactive way: Neuroimaging evidence for an approach-withdrawal framework

A growing body of literature shows that the emotional content of verbal material affects reading, wherein emotional words are given processing priority compared to neutral words. Human emotions can be conceptualised within a two-dimensional model comprised of emotional valence and arousal (intensity). These variables are at least in part distinct, but recent studies report interactive effects during implicit emotion processing and relate these to stimulus-evoked approach-withdrawal tendencies. The aim of the present study was to explore how valence and arousal interact at the neural level, during implicit emotion word processing. The emotional attributes of written word stimuli were orthogonally manipulated based on behavioural ratings from a corpus of emotion words. Stimuli were presented during an fMRI experiment while 16 participants performed a lexical decision task, which did not require explicit evaluation of a word′s emotional content. Results showed greater neural activation within right insular cortex in response to stimuli evoking conflicting approach-withdrawal tendencies (i.e., positive high-arousal and negative low-arousal words) compared to stimuli evoking congruent approach vs. withdrawal tendencies (i.e., positive low-arousal and negative high-arousal words). Further, a significant cluster of activation in the left extra-striate cortex was found in response to emotional than neutral words, suggesting enhanced perceptual processing of emotionally salient stimuli. These findings support an interactive two-dimensional approach to the study of emotion word recognition and suggest that the integration of valence and arousal dimensions recruits a brain region associated with interoception, emotional awareness and sympathetic functions.