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Posts Tagged ‘executive functions’

Do older adults benefit from videogames?

Brain training games claim to boost your mental skills. But while practicing a game might make you better at it, research in young people has shown it doesn’t improve how well you perform other cognitive tasks in everyday life. Now a new study suggests the case may be different for adults above the age of 60. Researchers at the University of California have designed a driving game called NeuroRacer. In this Nature Video, we see how the game can improve an older player’s short-term memory and attention, skills which decline with age.

Read the original research paper here:http://dx.doi.org/10.1038/nature12486 (from Nature)

“Owls” more likely to have ADHD?

07/12/2011 6 comments
Is there any relationship between chronotype and Attention-deficit hyperactivity disorder (ADHD) symptoms? Are evening oriented individuals more likely to have ADHD? This was the main question posed in a (relatively) recent article by Caci and colleagues.

ADHD is the most common neurodevelopmental disorder (Faraone et al., 2003) and affects about 3–6% of children (Tannock 1998). ADHD is defined by either an attentional dysfunction, hyperactive/impulsive behaviour or both (DSM-IV; American Psychiatric Association, 1994). Therefore, the diagnosis of ADHD has three subtypes: the Inattentive subtype (ADHD/IA), which is characterised by significant levels of inattention but subthreshold levels of hyperactive/ impulsive symptoms, the Hyperactive/Impulsive subtype (ADHD/HI), which is defined by hyperactivity/ impulsivity but not of inattention symptoms, and the Combined Inattentive-Hyperactive/Impulsive subtype (ADHD/C), which is characterised by maladaptive levels of both symptom clusters.

Morningness is a stable characteristic which reflects the phase of circadian system. It is a continuum with evening types at one end and morning types on the other. Previous studies have found that the evening orientation might be a risk factor for various disorders including depression and personality disorders. Morningness is also a heritable trait (Vink, Groot, Kerkhof, & Boomsma, 2001) and determined by genetic factors (Mishima, Tozawa, Satoh, Saitoh, & Mishima, 2005). Impulsivity and novelty seeking, two characteristics associated with particular ADHD subtypes are negatively related to morningness. Specifically, evening oriented individuals often score higher on tests assessing those traits. In addition to that, there is evidence that morningness is implicated in the variation of performance (Natale, Alzani, & Cicogna, 2003). Variability in various cognitive tasks is a common finding in many studies examining individuals with ADHD. Individuals with ADHD have also been found to experience a number of sleep related disorders such as sleep-onset difficulties, agitated sleep, and a higher number of nocturnal awakings.

Caci et al. examined the relationship between morningness and ADHD. Their hypothesis was that adults suspected of having ADHD are more evening oriented than are adults without ADHD. They recruited 354 participants and assessed their scores in the Composite Scale of Morningness (CSM), a measure of morningness, and the Adult Self-Report Scale v1.1 (ASRS), a self-reported questionnaire used for screening of ADHD in adults. ASRS includes two subscales for inattention and hyperactivity symptoms. This allowed Caci et al to examine the relationship between possible ADHD subtypes and morningness.

The results of the study confirmed the hypothesis; participants with higher scores on the ASRS reported having an evening orientation. The effect was stronger in participants with higher scores on the subscale of inattention. No correlation was found between hyperactivity and morningness. This provides evidence for the existence of different endophenotypes in ADHD. Since the sample used in this study consisted of healthy volunteers, it would be interesting to try to replicate this finding in diagnosed individuals with ADHD.

PS: After writing this post, I realised there’s a new study published in Nature by Baird et al. (2011) that examines endocrine and molecular levels of circadian rhythms in ADHD and seems to confirm the morningness hypothesis proposed by Caci et al. According to this paper, adult ADHD is accompanied by significant changes in the circadian system. I might write a post about it in the near future.

 

ResearchBlogging.orgCaci H, Bouchez J, & Baylé FJ (2009). Inattentive symptoms of ADHD are related to evening orientation. Journal of attention disorders, 13 (1), 36-41 PMID: 19387003

Investigating the Anatomical Relationship Between Primary Sensory and Prefrontal Cortices in the Human Brain

11/10/2011 1 comment

People experience the world in slightly different ways. Philosophers have been writing about this for years and, recently, studies using psychophysics and neuroimaging provide further support for this. A classic example is the way we perceive visual illusions; there is variability in the responses of people about the extent they experience various illusions. Schwarzkopf et al. (2010) showed that inter-individual differences in the surface area of V1 predict individual differences in conscious perception, such as how big something looks.

A study by Chen et al. that was published on the  JoN used a novel approach that combined non-invasive cortical functional mapping with whole-brain voxel-based morphometric analyses to investigate the anatomical relationship between the functionally mapped visual cortices and other cortical structures in healthy humans. Chen et al. found an interesting correlation between the size of V1 and primary auditory cortex. This relationship could be explained in terms of our everyday multisensory experience of the world. However, the size of those areas was anticorrelated with the size of the anterior prefrontal cortex (aPFC), the frontopolar part of the frontal cortex. In a few words, individuals with larger primary visual cortex had larger primary auditory cortex but smaller aPFC. This anticorrelation was only found for the primary sensory cortices and not for other visual cortices (e.g. V2, V3).

According to Chen et al.

…while one might expect a positive correlation between the whole-brain gray matter volume and the volume of its components, instead we found a striking anticorrelation for primary visual cortex: individuals with larger brains tended to have smaller primary visual cortices. In contrast, anterior prefrontal cortex was the single most enlarged region in a larger brain.

The aPFC is a particularly fascinating area. Apart from having many names (anterior PFC, the frontal pole, frontopolar cortex, rostral prefrontal cortex, BA 10…), aPFC is larger relative to the rest of the brain (Semendeferi et al., 2001) and is significantly different in humans compared to other primates (Semendeferi et al., 2001), suggesting that this region may contribute to the unique human behaviour. Furthermore, it is one of the last brain areas to mature in humans (Dumontheil et al., 2008) and has been recently identified as the region with the greatest relative prediction power about brain maturity over development (Dosenbach et al., 2011). Evidence from previous studies suggest that this particular area has a role in higher-order cognitive functions (including prospective memory)

The pairing between the expansion of anterior prefrontal cortex and the contraction of primary sensory cortices reflects a common ground for the formation of anatomically and phylogenetically remote cortical regions, and suggests the existence of a reciprocal link between high-order cognition and low-level sensation.

Future studies will attempt to further investigate this relationship and examine what the effects of these structural differences are on function and performance on various tests thought to tap on those areas.

ResearchBlogging.orgSong C, Schwarzkopf DS, Kanai R, & Rees G (2011). Reciprocal anatomical relationship between primary sensory and prefrontal cortices in the human brain. The Journal of neuroscience : the official journal of the Society for Neuroscience, 31 (26), 9472-80 PMID: 21715612

Schwarzkopf DS, Song C, & Rees G (2011). The surface area of human V1 predicts the subjective experience of object size. Nature neuroscience, 14 (1), 28-30 PMID: 21131954

Coren S, & Porac C (1987). Individual differences in visual-geometric illusions: predictions from measures of spatial cognitive abilities. Perception & psychophysics, 41 (3), 211-9 PMID: 3575080

Dumontheil I, Burgess PW, & Blakemore SJ (2008). Development of rostral prefrontal cortex and cognitive and behavioural disorders. Developmental medicine and child neurology, 50 (3), 168-81 PMID: 18190537

Semendeferi, K., Armstrong, E., Schleicher, A., Zilles, K., & Van Hoesen, G. W. (2001). Prefrontal cortex in humans and apes: a comparative study of area 10 American journal of physical anthropology, 3 (114), 224-241

Dosenbach NU, Nardos B, Cohen AL, Fair DA, Power JD, Church JA, Nelson SM, Wig GS, Vogel AC, Lessov-Schlaggar CN, Barnes KA, Dubis JW, Feczko E, Coalson RS, Pruett JR Jr, Barch DM, Petersen SE, & Schlaggar BL (2010). Prediction of individual brain maturity using fMRI. Science (New York, N.Y.), 329 (5997), 1358-61 PMID: 20829489

Behavioural Effects of Early Focal Damage to Prefrontal Cortex

18/04/2010 2 comments

ResearchBlogging.orgAnderson et al. (2007) report a case of a 14 month boy (PF1) who sustained damage to his right inferior dorsolateral prefrontal cortex due to resection of a vascular malformation on day 3 of life. After a successful surgery he exhibit normal behaviour and reached developmental milestones at a normal rate. Also, his performance on various clinical tests was normal, as well as his social and communication skills as rated by his mother. Compared to a sample of healthy controls PF1 was impaired significantly in the regulation of emotion and engagement of attention, specifically in unstructured conditions.
In particular, Anderson et al. (2007) report that:

PF1 showed
markedly high positive affectivity and low restraint
relative to his peers. This was particularly evident
in his intense and positive affective expressions
during free-flowing interactions, his unrestrained
approach of desirable but prohibited stimuli, and to
a lesser extent in his mildly atypical levels of anger
and resistance when physically restrained. Faced
with problem-solving tasks, when most of his peers
displayed affectively neutral expressions and
focused on finding the solutions, PF1 initially
responded with strong and under-regulated positive
emotion that interfered with attentional engagement
on the task at hand.

According to the writers the results of the study provide useful information about the impact that early damage in the prefrontal cortex may have on emotional and cognitive behaviour. I’m looking forward to their future reports on this particular case as the boy grows up.

Anderson SW, Aksan N, Kochanska G, Damasio H, Wisnowski J, & Afifi A (2007). The earliest behavioral expression of focal damage to human prefrontal cortex. Cortex; a journal devoted to the study of the nervous system and behavior, 43 (6), 806-16 PMID: 17710831

Prospective Memory in ASD

25/03/2010 3 comments

ResearchBlogging.orgProspective Memory (PM or ProM- I’ll be using the term PM) is defined as a number of functions that enable a person to carry out an intended act after a delay (Burgess et al., 2001). A significant number (50–80%) of all everyday memory problems are, at least in part, PM problems (Kliegel & Martin, 2003). However, PM is one of the least studied forms of memory in cognitive neuroscience.

PM is divided into a retrospective and a prospective component (Einstein & McDaniel, 1990). The retrospective component involves the retention of the action to be performed and the prospective entails the retrieval of the action, after the identification of the encoded cue. Both frontal lobe areas and the medial temporal lobes (MTL) are thought to play a role in PM. One area constantly associated with PM tasks from various lesions and neuroimaging studies (Simons et al., 2006; Miller & Cohen, 2001) is the frontopolar and superior rostral aspects of the frontal lobes (approximating BA10).

A number of cognitive abilities that have been associated with rostral PFC seem to be impaired in ASD (Hill, 2004; also see older post on Executive Functions in ASD.)

Even though evidence suggests that PM could be impaired in ASD, only a limited number of studies have been done to examine this. Mackinlay et al. (2006) investigated PM in children with ASD and found that they had difficulties in planning, carrying out and switching between different tasks.

Recently, Altgassen et al. (2009) found reduced performance in ASD as compared to controls in a time-based PM task and that was attributed to poor task monitoring and task organization. Monitoring, like many executive functions, also is associated with frontal lobe function (Shallice & Burgess, 1991).

Only one study (Altgassen et al., 2009b) has looked into event-based PM on children with ASD. The participants were 19 high-functioning children and adolescents with ASD and 19 typically developing controls. They were asked to work simultaneously on an ongoing and a PM task. The ongoing task was a visuo-spatial working memory task and for the PM task, they were to press the certain key whenever the background colour of the screen changed to yellow. Dependent measures were accuracy and reaction times. They also measured subjective everyday executive functioning by using The DEX questionnaire, which was filled by the parents of the subjects. No significant differences were found between the two groups in any of the measures apart from the subjective everyday ratings. The parents of the participants with ASD rated their children’s performance as poorer than controls’ parents.

Here’s the explanation that Altgassen et al. (2009b) give about the deficits found in time-based PM, but not in event-based PM:

…in comparison to time-based tasks or complex multitasking paradigms simple, event-based PM tasks are very structured, and similarly to cued (retrospective) recall provide (here: visual) cues that may support retrieval of the intended action and put lower demands on self-initiated strategy application which may decrease executive control demands and thus enable individuals with ASD to preserved event-based PM
performance [23]…

Interestingly, studies show that people with ASD seem to have deficits mostly in ill-structured tasks, while they perform near or at control levels at well-structured tests (White et al., 2009). In this paper

the ASD group tended to create fewer spontaneous strategies and exhibit more idiosyncratic behavior, which particularly disadvantaged them on the more open-ended tasks.

It would be very interesting to see if future studies will replicate Altgassen et al.’s results using a bigger sample or a more difficult task requiring higher working memory load.

Altgassen, M., Schmitz-Hübsch, M., & Kliegel, M. (2009). Event-based prospective memory performance in autism spectrum disorder Journal of Neurodevelopmental Disorders, 2 (1), 2-8 DOI: 10.1007/s11689-009-9030-y

Executive Functions in ASD

braincopyThere are three key theories that attempt to explain the links between brain and behaviour in Autistic spectrum disorders (ASD): the Theory of Mind Deficit Hypothesis (for a review see Baron-Cohen, 2001), the Weak Central Coherence (Happé & Frith, 2006) and that of Executive Dysfunction (Hill, 2004).

Executive functions is an umbrella term for a number of cognitive and behavioural capacities such as planning, working memory, inhibition, mental flexibility, multitasking, initiation and monitoring of action (Gilbert & Burgess, 2008). Executive functions are usually impaired in patients with frontal lobe damage and in many neurodevelopmental disorders like ADHD, OCD, schizophrenia and ASD.  These disorders are likely to involve deficits in the frontal lobes.

Autistic people seem to be impaired only in some tests of executive functions, especially those involving multitasking (“Six Element Test”, Hill & Bird, 2006), planning (“Tower of London”, Ozonoff et al, 1991) and Inhibition (“Go/No-Go task” ,  Ozonoff & Strayer, 1997). Deficits have also been shown in planning and abstract problem solving tasks (Hill & Bird, 2006). On other tests their performance is equal or superior to control groups (Minshew, Goldstein & Siegel, 1997). It’s worth noting that ASD individuals are mostly impaired in newer tests rather than classical tests of executive functions (Hill & Bird, 2006, Gilbert et al., 2008). These findings could be due to the heterogeneity of different tests of executive function (Gilbert et al., 2008).

Most of the tasks in which ASD individuals show deficits are thought to be mediated by the frontal lobes. A number of studies have identified several several cortical, subcortical abnormalities and functional differences (Kawakubo et al., 2009; Schmitz et al., 2005).

The theory of cortical underconnectivity  posits a deficit in integration of information at the neural and cognitive levels (Just et al., 2006). Findings from neuroimaging studies such as the thinning of the corpus callosum and the reduced connectivity, especially with the frontal areas and also the fusiform face area in ASD people support the theory of underconnectivity (Hughes, 2007). Recently, increased activation in medial rostral prefrontal cortex (BA 10) during tasks of stimulus-oriented versus stimulus-independent attention has been found in people with ASD (Gilbert et al., 2008). Previous studies has shown the importance of rPFC in selection between stimulus-oriented and stimulus-independent thought (Gilbert, Frith & Burgess, 2005; Ramnani & Owen, 2004). On the same task the control group showed greater activity primarily in bilateral occipital cortex. According to Gilbert et al.:

“This suggests that the control group were able to modulate activity in early visual cortex according to the attentional demands of the task to a greater degree than the ASD group. The stimuli were matched between the two conditions, suggesting attentional modulation rather than an effect of stimulus-category. This finding is consistent with the suggestion of functional underconnectivity in ASD”

Further Readings

Happé, F., & Frith, U. (1996). The neuropsychology of autism.Brain, 19, 1377-1400.

White, S., O’Reilly, H., & Frith, U. (2009). Big heads, small details and autism. Neuropsychologia, 47(5), 1274-1281.‎

Mundy, P. (2003). The Neural Basis of Social Impairments in Autism: The Role of the Dorsal Medial-Frontal Cortex and Anterior Cingulate System. Journal of Child Psychology & Psychiatry, 44, 793-809

Happé, F., Booth, R., Charlton, R. & Hughes, C. (2006) Executive function deficits in Autism Spectrum Disorders and Attention-Deficit/Hyperactivity Disorder: Examining profiles across domains and ages. Brain and Cognition.

Baron-Cohen, S., & Swettenham, J. (1998) Theory of mind in autism: Its relationship to executive function and central coherence. In D.J. Cohen & F.R. Volkmar (Eds.), Handbook of autism and pervasive developmental disorders (2nd ed., pp. 880–893). New York: Wiley.

Martin, I. and McDonald, S. (2003). Weak coherence, no theory of mind, or executive dysfunction? solving the puzzle of pragmatic language disorders. Brain and language, 85(3):451-466.

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