Why is the prefrontal cortex so important?

Why is the prefrontal cortex so important?

Credit: Medium.com

Credit: Medium.com

The prefrontal cortex is located in our frontal lobe, the part of our brain at the very front of our head.  The prefrontal cortex is involved in executive functions, or the higher cognitive functions, of our brain. Executive functions act as the chief’s executive officer and include memory, attention, flexibility, planning, and problem solving. For example, the prefrontal cortex is involved in decision making by considering past events and experiences in order to make the best choices. The prefrontal cortex also plays a role in short term memory. It also affects things like holding conversations, reasoning, self-monitoring and time management.

The prefrontal cortex is one of the slowest parts of the brain to develop, only reaching full maturity in our mid-twenties. This can explain why children and teenagers are more prone to risk-taking behaviour, while adults are generally better at planning ahead and reasoning.

Individuals who suffer damage to the prefrontal cortex will often continue to have normal movement abilities and intelligence. However, they frequently display difficulties with executive functions such as memory and attention. Damage to the prefrontal cortex can also cause personality changes, abnormal emotional responses, and difficulty in functioning in daily life.

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Phineas Gage is a classic neuropsychological example of the effects of prefrontal cortex damage. Gage was a railroad worker who suffered an accident in which a metal rod was driven through his frontal lobe. He survived the accident, but his friends remarked that his personality changed drastically – he was “no longer Gage”. Recently, it has been debated as to whether the extent of Gage’s transformation has been exaggerated (read more here: https://thepsychologist.bps.org.uk/volume-21/edition-9/phineas-gage-unravelling-myth).

As the prefrontal cortex is linked to so many critical functions – memory, attention, decision making, reasoning – it is clear that it is an important part of our brain, particularly for children. The development of the prefrontal cortex is essential for young children to begin to engage with and navigate the world around them.

Our research looks at attention in children at risk for ADHD. We are currently running a study for babies aged 10-20 months. If you would like more information, or would like to take part, please email sarah.conroy1@ucd.ie or fill out the form on our  homepage!


Looking at attention

ADHD is associated with poor attention control, the markers of which include reduced inhibition and cognitive flexibility. These refer to the capacity to ignore irrelevant or distracting objects, and the ability to disengage attention from one object and focusing on another, respectively. Laboratory tasks designed to measure these cognitive processes typically involve showing an object on a computer screen, along with other distracting objects that are designed to capture participants’ attention.

In our lab, participants’ attention can be observed using an eye-tracker, which allows us to determine the location on the computer screen that is being focused on at any given moment. This is especially useful in infant research as it is unobtrusive and does not require any overt responses from the participant, like pressing buttons or answering questions. During an eye-tracking session, infants are sat either on their parent’s lap or in a highchair, while viewing moving images on a computer screen.

The eye-tracking system, attached below the monitor, records infants’ eye movements while they view the images on the screen.

The eye-tracking system, attached below the monitor, records infants’ eye movements while they view the images on the screen.

The eye-tracking system is made up of projectors that shines infrared light (invisible to humans) and cameras that records the reflection of the light on the eyes. This reflection pattern changes slightly as the eyes rotate and move around while looking at different areas of the screen. The eye-tracker is able to use this to calculate the location of focus throughout the session.

A recording of gaze locations being tracked while a participant is looking at a scene

A recording of gaze locations being tracked while a participant is looking at a scene

This allows us to collect information such as the pattern of gazes, the amount of time spent looking at specific objects, and even changes in pupil size, which are then used as measures of inhibition and cognitive flexibility.

A (Brief) History of ADHD

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by persistent symptoms of inattention, impulsivity, and hyperactivity. These symptoms must cause significant impairment in social, academic, or occupational functioning. It is prevalent worldwide, with prevalence estimates ranging from 1-5%. Yet how did scientists come to this definition of ADHD? This article will offer a brief glimpse of the history of ADHD, from its early beginnings in the mid-19th century up to today.

One of the earliest reports of ADHD in the literature comes from an anecdotal children’s story by Heinrich Hoffman. Hoffman’s 1884 story is believed to be describing a young boy known as ‘Fidgety Phil’ with ADHD-like symptoms causing a fuss at dinner time.

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The 1902 lectures by Sir George Frederic Still are considered by many scientists and researchers to be the scientific starting point of the history of ADHD. Still talked about a defect of moral control in a group of children – who lacked “the control of an action in conformity with the idea of the good of all”. Still also remarked that this particular group of children had no “general impairment of intellect” i.e. they were children of average intelligence with no major deficits. His patients were also reported as having an abnormal incapacity for sustained attention by both parents and teachers. This relates to the current ADHD criteria for ADHD symptoms to be present in more than one setting (for example, at home and at school).

Franz Kramer and Hans Pollnow reported on a hyperkinetic disease in infancy, of which the most characteristic symptom was motor restlessness. Kramer and Pollnow noted that patients had remarkable motor activity which appeared to be very urgent. This can be related to today’s concept of hyperactivity. Patients were also reported to not be able to remain still for prolonged periods of time. This is similar to the American Psychiatric Association’s description of children with ADHD as being “driven by a motor” (2000). Kramer and Pollnow also make references to distractibility, and patients having difficulty completing tasks or concentrating.



Credit: © Rawpixel / Fotolia

Credit: © Rawpixel / Fotolia

In 1937, Charles Bradely reported a positive effect of stimulant medication in children with various behaviour disorders. He discovered that the stimulant Benzedrine was most likely to benefit children with short attention spans, dyscalculia, mood lability, hyperactivity, impulsiveness, and poor memory. As such, this was the first use of stimulant medication as a treatment for ADHD.

Scientists discovered a pattern of hyperactivity being related to reports of brain damage in children. Research in the 1930s and 1940s supported the idea of a causal connection between brain damage and abnormal behaviour. Thus, the idea emerged that minimal brain damage to the brain could cause hyperactive behaviour. Researcher Alfred Strauss considered the symptom of hyperactivity to be a sufficient diagnostic sign of underlying brain damage. Further, Strauss argued that hyperactivity could be able to distinguish between brain-injured and non-brain-injured children.

Criticism began to arise over the necessity of the brain to be damaged in hyperactive children. Laufer and colleagues proposed that there may be a functional disturbance in the brain, rather than damage. Clements (1966) specified the three symptoms of  an inability to control attention, impulsivity, and motor function. Thus, the three core symptoms characterizing ADHD of inattention, impulsivity, and hyperactivity were established with the definition of minimal brain dysfunction.

From the 1960s, criticism of minimal brain dysfunction arose. It was criticised for being too general. Minimal brain dysfunction was later replaced with more specific labels such as hyperactivity, learning disability, dyslexia, or language disorder. In the Diagnostic and Statistical Manual of Mental Disorders (DSM) 2nd edition (a manual used to diagnose most mental illnesses), hyperactivity was referred to as being “characterised by over-activity, restlessness, distractibility, and short attention span” (APA, 1968).

In the 1970s, the focus shifted more to the issues of attention, rather than hyperactivity. This shift was aided by an influential paper by Virginia Douglas in 1972. As a result, the publication of DSM-III in 1980 saw the introduction of a new disorder – attention deficit disorder with or without hyperactivity. The DSM-III contained three separate symptom lists for inattention, impulsivity, and hyperactivity. In the DSM-III-R (APA, 1987) attention deficit hyperactivity disorder became a single disorder, with all symptoms combined into a single list. The DSM-IV (APA, 1994) divided ADHD into three subtypes: (i) ADHD – inattentive subtype, (ii) ADHD – hyperactive subtype, and (iii) ADHD – combined subtype. It was also in the 1990s that ADHD was recognised as not being an exclusively childhood disorder which disappeared with age. It was instead recognised that ADHD was a chronic persistent disorder remaining into adulthood in many cases. However, it was only with the release of DSM-V (APA, 2013) that ADHD was officially recognised in adults.

How does our research fit in?

The UCD Neuropsychology Lab is currently conducting a study looking at potential early markers for ADHD. We are particularly interested in sleep, sensory processing, and family functioning and their relation with ADHD. For our study, we are recruiting children under 6 who have a parent or older sibling with a diagnosis of ADHD. If you would like to take part, you can click on the ‘How Do I Take Part?’ tab at the top of the screen!



How do we measure sleep?

Since our upcoming project is studying the role of sleep in attention development, one of the most important pieces of new equipment in the lab are our sleep actigraphs. These nifty gadgets record movement and when worn through the night, are able to measure the amount and quality of sleep.

The actigraphs that participants will wear

The actigraphs that participants will wear

 

We recently recruited an honorary research assistant to help demonstrate how easy it is to collect the sleep data with the actigraphs and what information can be gleaned from it.


Research Assistant Charlotte inspecting the actigraph before giving it her seal of approval

Research Assistant Charlotte inspecting the actigraph before giving it her seal of approval

Using the actigraph is extremely simple. Just put it on the ankle of our infant participants, like you would a watch, and the actigraph will start recording automatically. There are no lights, beeps or buzzes to interfere with regular day-to-day activity and the only input we require is for the grown-ups to note down what time the infants went to bed and got up the next morning.

When the actigraph is brought back to the lab, the data will be downloaded from it and we will be able to chart the sleep patterns, and calculate the quality of sleep.


Charts showing amount of movement during sleep (top), sleep/awake periods (middle), and periods of active sleep phase during the sleep cycle (bottom)

Charts showing amount of movement during sleep (top), sleep/awake periods (middle), and periods of active sleep phase during the sleep cycle (bottom)

Some of the measures that can be extracted and compared to other participants

Some of the measures that can be extracted and compared to other participants

One of the aims of the study is to investigate the influence of infant sleep behaviour on attention development in young children and the data collected using the actigraphs is a key component in this. The study hopes to help us better understand attentional disorders such as ADHD and potentially lead to the development of early interventions in the future.