Reductions in prefrontal activation predict off-topic utterances during speech production

The ability to speak coherently is essential for effective communication, but little is known about the neural systems that support coherence. Here, the authors show that activity in two prefrontal cortex regions, BA10 and BA45, predicts the level of coherence in the speech of healthy older adults

Sequential then interactive processing of letters and words in the left fusiform gyrus

Despite decades of cognitive, neuropsychological, and neuroimaging studies, it is unclear if letters are identified prior to word-form encoding during reading, or if letters and their combinations are encoded simultaneously and interactively. Here, using functional magnetic resonance imaging, we show that a ‘letter-form’ area (responding more to consonant strings than false fonts) can be distinguished from an immediately anterior ‘visual word-form area’ in ventral occipitotemporal cortex (responding more to words than consonant strings). Letter-selective magnetoencephalographic responses begin in the letter-form area ~60ms earlier than word-selective responses in the word-form area. Local field potentials confirm the latency and location of letter-selective responses. This area shows increased high gamma power for ~400ms, and strong phase-locking with more anterior areas supporting lexico-semantic processing. These findings suggest that during reading, visual stimuli are first encoded as letters before their combinations are encoded as words. Activity then rapidly spreads anteriorly, and the entire network is engaged in sustained integrative processing

The substrate that dreams are made on: An evaluation of current neurobiological theories of dreaming

Theories regarding ambiguous consciousness states, such as dreaming, often attract questions regarding the scientific status of the experiments on which they are based. Rarely, however is the scientific status of the theory itself scrutinized. There are basic principles of theory construction that can provide a framework for evaluating current neurobiological theories of dreaming. This chapter places particular emphasis on the activation-synthesis (AS) and activation, input and modulation (AIM) models, developed by Hobson and colleagues over the past three decades (Hobson and McCarley, Am J Pschiatry 134:1335-1348, 1977; Hobson et al., Behav Brain Sci 23:793-842, 2000). This theory set was chosen as it can be considered one of the most widely cited and publicized neurobiological theories of dreaming today. Our aim in this chapter is not to criticize this work specifically, but to draw attention to the problems of theory development presently inherent in all dream research. The nature of the assumptions which underlie dream theories, the logic of argument, and the validity of methodologies used in collecting the empirical evidence, are scrutinized according to principles of theory construction and validity. We argue that modern theories of dreaming, whilst evolving ad hoc modifications in the face of new and sometimes anomalous evidence, are essentially unfalsifiable, and by definition do not qualify as scientific theories. However, as methodologies and technologies improve, particularly in the areas of sleep stage recording and neuroimaging, a new paradigm for the neurobiology of dreaming may emerge