Growth without growth hormone and similar dysmorphic features in three patients with sporadic combined pituitary hormone deficiencies

BACKGROUND/AIMS

Mutations in the HESX1 gene are associated with a broad spectrum of phenotypes: septo-optic dysplasia, midline defects, pituitary abnormalities with consequent hypopituitarism, isolated growth hormone (GH) deficiency or combined pituitary hormone deficiencies (CPHD). This study examined the prevalence of mutations in the HESX1 gene in patients with CPHD.

PATIENTS/METHODS

Sixty patients with sporadic CPHD without septo-optic dysplasia were screened for mutations in HESX1.

RESULTS

Three patients were found to be heterozygous for the same Asn125Ser variant in the HESX1 gene. In all 3, panhypopituitarism was presented in the neonatal period, manifested by severe hypoglycemia and neonatal jaundice in 2 patients and respiratory distress in 1. Remarkable findings from physical examination included coarse face; prominent, large, low-set ears; and skeletal abnormalities. Magnetic resonance imaging, performed in 2 patients, revealed a hypoplastic anterior and ectopic posterior pituitary without other midline anomalies. Despite persistent GH deficiency and undetectable levels of insulin-like growth factor 1, all patients had normal linear growth along the 10-25th percentile without GH therapy.

CONCLUSION

The present study expands the clinical picture of HESX1 mutations by demonstrating that patients heterozygous for Asn125Ser may have a severe endocrinologic and neuroradiologic phenotype and similar dysmorphic features appearing very early in life.

A cognitive neuroscience hypothesis of mood and depression

Although mood has a direct impact on mental and physical health, our understanding of the mechanisms underlying mood regulation is limited. Here, I propose that there is a direct reciprocal relation between the cortical activation of associations and mood regulation, whereby positive mood promotes associative processing, and associative processing promotes positive mood. This relation might stem from an evolutionary pressure for learning and predicting. Along these lines, one can think of mood as a reward mechanism that guides individuals to use their brains in the most productive manner. The proposed framework has many implications, most notably for diagnosing and treating mood disorders such as depression; for elucidating the role of inhibition in the regulation of mood; for contextualizing adult hippocampal neurogenesis; and for a general, non-invasive improvement of well-being.

See it with feeling: affective predictions during object perception

People see with feeling. We 'gaze', 'behold', 'stare', 'gape' and 'glare'. In this paper, we develop the hypothesis that the brain's ability to see in the present incorporates a representation of the affective impact of those visual sensations in the past. This representation makes up part of the brain's prediction of what the visual sensations stand for in the present, including how to act on them in the near future. The affective prediction hypothesis implies that responses signalling an object's salience, relevance or value do not occur as a separate step after the object is identified. Instead, affective responses support vision from the very moment that visual stimulation begins.

The proactive brain: memory for predictions

It is proposed that the human brain is proactive in that it continuously generates predictions that anticipate the relevant future. In this proposal, analogies are derived from elementary information that is extracted rapidly from the input, to link that input with the representations that exist in memory. Finding an analogical link results in the generation of focused predictions via associative activation of representations that are relevant to this analogy, in the given context. Predictions in complex circumstances, such as social interactions, combine multiple analogies. Such predictions need not be created afresh in new situations, but rather rely on existing scripts in memory, which are the result of real as well as of previously imagined experiences. This cognitive neuroscience framework provides a new hypothesis with which to consider the purpose of memory, and can help explain a variety of phenomena, ranging from recognition to first impressions, and from the brain's 'default mode' to a host of mental disorders.

Cultural specificity in amygdala response to fear faces

The human amygdala robustly activates to fear faces. Heightened response to fear faces is thought to reflect the amygdala's adaptive function as an early warning mechanism. Although culture shapes several facets of emotional and social experience, including how fear is perceived and expressed to others, very little is known about how culture influences neural responses to fear stimuli. Here we show that the bilateral amygdala response to fear faces is modulated by culture. We used functional magnetic resonance imaging to measure amygdala response to fear and nonfear faces in two distinct cultures. Native Japanese in Japan and Caucasians in the United States showed greater amygdala activation to fear expressed by members of their own cultural group. This finding provides novel and surprising evidence of cultural tuning in an automatic neural response.

The cortical underpinnings of context-based memory distortion

Everyday contextual settings create associations that later afford generating predictions about what objects to expect in our environment. The cortical network that takes advantage of such contextual information is proposed to connect the representation of associated objects such that seeing one object (bed) will activate the visual representations of other objects sharing the same context (pillow). Given this proposal, we hypothesized that the cortical activity elicited by seeing a strong contextual object would predict the occurrence of false memories whereby one erroneously "remembers" having seen a new object that is related to a previously presented object. To test this hypothesis, we used functional magnetic resonance imaging during encoding of contextually related objects, and later tested recognition memory. New objects that were contextually related to previously presented objects were more often falsely judged as "old" compared with new objects that were contextually unrelated to old objects. This phenomenon was reflected by activity in the cortical network mediating contextual processing, which provides a better understanding of how the brain represents and processes context.

Integrated contextual representation for objects' identities and their locations

Visual context plays a prominent role in everyday perception. Contextual information can facilitate recognition of objects within scenes by providing predictions about objects that are most likely to appear in a specific setting, along with the locations that are most likely to contain objects in the scene. Is such identity-related ("semantic") and location-related ("spatial") contextual knowledge represented separately or jointly as a bound representation? We conducted a functional magnetic resonance imaging (fMRI) priming experiment whereby semantic and spatial contextual relations between prime and target object pictures were independently manipulated. This method allowed us to determine whether the two contextual factors affect object recognition with or without interacting, supporting a unified versus independent representations, respectively. Results revealed a Semantic x Spatial interaction in reaction times for target object recognition. Namely, significant semantic priming was obtained when targets were positioned in expected (congruent), but not in unexpected (incongruent), locations. fMRI results showed corresponding interactive effects in brain regions associated with semantic processing (inferior prefrontal cortex), visual contextual processing (parahippocampal cortex), and object-related processing (lateral occipital complex). In addition, activation in fronto-parietal areas suggests that attention and memory-related processes might also contribute to the contextual effects observed. These findings indicate that object recognition benefits from associative representations that integrate information about objects' identities and their locations, and directly modulate activation in object-processing cortical regions. Such context frames are useful in maintaining a coherent and meaningful representation of the visual world, and in providing a platform from which predictions can be generated to facilitate perception and action.

Magnocellular projections as the trigger of top-down facilitation in recognition

Object recognition is traditionally viewed as a hierarchical, bottom-up neural process. This view has been challenged recently by theoretical models and by findings indicating that top-down processes are involved in facilitating recognition. However, how such high-level information can be activated quickly enough to facilitate the bottom-up processing is yet unknown. We propose that such top-down facilitation is triggered by magnocellular information projected early and rapidly to the orbitofrontal cortex. Using human neuroimaging, we show that stimuli designed to bias processing toward the magnocellular pathway differentially activated the orbitofrontal cortex compared with parvocellular-biased stimuli. Although the magnocellular stimuli had a lower contrast than the parvocellular stimuli, they were recognized faster and just as accurately. Moreover, orbitofrontal activity predicted the performance advantage for the magnocellular, but not for the parvocellular-biased, stimuli, whereas the opposite was true in the fusiform gyrus. Last, analyses of effective connectivity using dynamic causal modeling showed that magnocellular-biased stimuli significantly activated pathways from occipital visual cortex to orbitofrontal cortex and from orbitofrontal cortex to fusiform gyrus. Conversely, parvocellular-biased stimuli significantly activated a pathway from the occipital visual cortex to fusiform gyrus. Our findings support the proposal that fast magnocellular projections linking early visual and inferotemporal object recognition regions with the orbitofrontal cortex facilitate object recognition by enabling the generation of early predictions.

Top-down predictions in the cognitive brain

The human brain is not a passive organ simply waiting to be activated by external stimuli. Instead, we propose that the brain continuously employs memory of past experiences to interpret sensory information and predict the immediately relevant future. The basic elements of this proposal include analogical mapping, associative representations and the generation of predictions. This review concentrates on visual recognition as the model system for developing and testing ideas about the role and mechanisms of top-down predictions in the brain. We cover relevant behavioral, computational and neural aspects, explore links to emotion and action preparation, and consider clinical implications for schizophrenia and dyslexia. We then discuss the extension of the general principles of this proposal to other cognitive domains.

The proactive brain: using analogies and associations to generate predictions

Rather than passively 'waiting' to be activated by sensations, it is proposed that the human brain is continuously busy generating predictions that approximate the relevant future. Building on previous work, this proposal posits that rudimentary information is extracted rapidly from the input to derive analogies linking that input with representations in memory. The linked stored representations then activate the associations that are relevant in the specific context, which provides focused predictions. These predictions facilitate perception and cognition by pre-sensitizing relevant representations. Predictions regarding complex information, such as those required in social interactions, integrate multiple analogies. This cognitive neuroscience framework can help explain a variety of phenomena, ranging from recognition to first impressions, and from the brain's 'default mode' to a host of mental disorders.

Top-down facilitation of visual object recognition: object-based and context-based contributions

The neural mechanisms subserving visual recognition are traditionally described in terms of bottom-up analysis, whereby increasingly complex aspects of the visual input are processed along a hierarchical progression of cortical regions. However, the importance of top-down facilitation in successful recognition has been emphasized in recent models and research findings. Here we consider evidence for top-down facilitation of recognition that is triggered by early information about an object, as well as by contextual associations between an object and other objects with which it typically appears. The object-based mechanism is proposed to trigger top-down facilitation of visual recognition rapidly, using a partially analyzed version of the input image (i.e., a blurred image) that is projected from early visual areas directly to the prefrontal cortex (PFC). This coarse representation activates in the PFC information that is back-projected as "initial guesses" to the temporal cortex where it presensitizes the most likely interpretations of the input object. In addition to this object-based facilitation, a context-based mechanism is proposed to trigger top-down facilitation through contextual associations between objects in scenes. These contextual associations activate predictive information about which objects are likely to appear together, and can influence the "initial guesses" about an object's identity. We have shown that contextual associations are analyzed by a network that includes the parahippocampal cortex and the retrosplenial complex. The integrated proposal described here is that object- and context-based top-down influences operate together, promoting efficient recognition by framing early information about an object within the constraints provided by a lifetime of experience with contextual associations.

Visual elements of subjective preference modulate amygdala activation

What are the basic visual cues that determine our preference towards mundane everyday objects? We previously showed that a highly potent cue is the nature of the object's contour: people generally like objects with a curved contour compared with objects that have pointed features and a sharp-angled contour. This bias is hypothesized here to stem from an implicit perception of potential threat conveyed by sharp elements. Using human neuroimaging to test this hypothesis, we report that the amygdala, a brain structure that is involved in fear processing and has been shown to exhibit activation level that is proportional to arousal in general, is significantly more active for everyday sharp objects (e.g., a sofa with sharp corners) compared with their curved contour counterparts. Therefore, our results indicate that a preference bias towards a visual object can be induced by low-level perceptual properties, independent of semantic meaning, via visual elements that on some level could be associated with threat. We further present behavioral results that provide initial support for the link between the sharpness of the contour and threat perception. Our brains might be organized to extract these basic contour elements rapidly for deriving an early warning signal in the presence of potential danger.

The units of thought

That associative processing provides the vehicle of thought is a long-standing idea. We describe here observations from cognitive neuroimaging that elucidate the neural processing that mediates this element. This account further allows a more specific ascription of a cognitive function to the brain's "default" activity in mindwandering. We extend this account to argue that one primary outcome of associative processing is the generation of predictions, which approximate the immediately relevant future and thus facilitate perception, action, and the progression of thought.

Temporally extended gene expression of the ADP-Glc pyrophosphorylase large subunit (AgpL1) leads to increased enzyme activity in developing tomato fruit

Tomato plants (Solanum lycopersicum) harboring the allele for the AGPase large subunit (AgpL1) derived from the wild species Solanum habrochaites (AgpL1 ( H )) are characterized by higher AGPase activity and increased starch content in the immature fruit, as well as higher soluble solids in the mature fruit following the breakdown of the transient starch, as compared to fruits from plants harboring the cultivated tomato allele (AgpL1 ( E )). Comparisons of AGPase subunit gene expression and protein levels during fruit development indicate that the increase in AGPase activity correlates with a prolonged expression of the AgpL1 gene in the AgpL1 ( H ) high starch line, leading to an extended presence of the L1 protein. The S1 (small subunit) protein also remained for an extended period of fruit development in the AgpL1 ( H ) fruit, linked to the presence of the L1 protein. There were no discernible differences between the kinetic characteristics of the partially purified AGPase-L1(E) and AGPase-L1(H) enzymes. The results indicate that the increased activity of AGPase in the AgpL1 ( H ) tomatoes is due to the extended expression of the regulatory L1 and to the subsequent stability of the heterotetramer in the presence of the L1 protein, implying a role for the large subunit not only in the allosteric control of AGPase activity but also in the stability of the AGPase L1-S1 heterotetramer. The introgression line of S. lycopersicum containing the wild species AgpL1 ( H ) allele is a novel example of transgressive heterosis in which the hybrid multimeric enzyme shows higher activity due to a modulated temporal expression of one of the subunits.

The influence of nonremembered affective associations on preference

An important influence on our preference toward a specific object is its associations with affective information. Here, the authors concentrate on the role of memory on shaping such preferences. Specifically, the authors used a multistage behavioral paradigm that fostered associations between neutral shapes and affective images. Participants that explicitly remembered these affective associations preferred neutral shapes associated with positive images. Counterintuitively, participants who could not explicitly remember the associations preferred neutral shapes that were associated with negative images. Generally, the difference in preference between participants who could and could not remember the affective associations demonstrates a critical link between memory and preference formation. The authors propose that the preference for negatively associated items is a manifestation of a mechanism that produces an inherent incentive for rapidly assessing potentially threatening aspects in the environment.

Humans prefer curved visual objects

People constantly make snap judgments about objects encountered in the environment. Such rapid judgments must be based on the physical properties of the targets, but the nature of these properties is yet unknown. We hypothesized that sharp transitions in contour might convey a sense of threat, and therefore trigger a negative bias. Our results were consistent with this hypothesis. The type of contour a visual object possesses--whether the contour is sharp angled or curved--has a critical influence on people's attitude toward that object.

The Parahippocampal Cortex Mediates Spatial and Nonspatial Associations

The parahippocampal cortex (PHC) has been implicated in the processing of place-related information. It has also been implicated in episodic memory, even for items that are not related to unique places. How could the same cortical region mediate such seemingly different cognitive processes? Both processes rely on contextual associations, and we therefore propose that the PHC should be viewed not as exclusively dedicated for analyzing place-related information, or as solely processing episodic memories, but instead as more generally playing a central role in contextual associative processing. To test this proposal, we created a novel learning paradigm to form new associations among meaningless visual patterns. These new associations were created to emulate either spatial or nonspatial contexts. Both spatial and nonspatial associations activated the PHC more than noncontextual items. Moreover, items from spatial contexts activated the posterior part of the PHC, whereas items from nonspatial contexts activated the anterior PHC. Therefore, we show that the PHC plays a role of processing contextual associations in general, and that these associations are not restricted to spatial information. By modifying the existing view of the PHC function accordingly, the seemingly contradicting processes that activate it can be reconciled under one overarching framework.

Top-down facilitation of visual recognition

Cortical analysis related to visual object recognition is traditionally thought to propagate serially along a bottom-up hierarchy of ventral areas. Recent proposals gradually promote the role of top-down processing in recognition, but how such facilitation is triggered remains a puzzle. We tested a specific model, proposing that low spatial frequencies facilitate visual object recognition by initiating top-down processes projected from orbitofrontal to visual cortex. The present study combined magnetoencephalography, which has superior temporal resolution, functional magnetic resonance imaging, and a behavioral task that yields successful recognition with stimulus repetitions. Object recognition elicited differential activity that developed in the left orbitofrontal cortex 50 ms earlier than it did in recognition-related areas in the temporal cortex. This early orbitofrontal activity was directly modulated by the presence of low spatial frequencies in the image. Taken together, the dynamics we revealed provide strong support for the proposal of how top-down facilitation of object recognition is initiated, and our observations are used to derive predictions for future research.