Attention Deficit Hyperactivity Disorder (ADHD) is commonly associated with difficulties in attention, organization, and impulse control. However, according to psychiatrist and brain imaging researcher Daniel Amen, ADHD is not a single condition. Through thousands of SPECT brain scans, he proposed several ADD/ADHD subtypes that show different patterns of brain activity.
One brain network that has received increasing attention in ADHD research is the Default Mode Network (DMN). Although the DMN is not a single brain structure, it consists of interconnected regions that become active when the mind is not focused on an external task.
According to Dr. Amen's observations and broader ADHD research, differences in how attention networks interact with the Default Mode Network may help explain why some individuals struggle with distraction while others become trapped in persistent thoughts and mental rigidity.
What Is the Default Mode Network?
The Default Mode Network is a collection of brain regions that tend to become active during:
- Daydreaming
- Mind wandering
- Self-reflection
- Remembering the past
- Imagining the future
- Internal thinking
Key regions associated with the DMN include:
- The medial prefrontal cortex
- The posterior cingulate cortex
- The precuneus
- Parts of the parietal cortex
- The hippocampal network
When a person begins focusing on a task, the DMN normally becomes less active while attention networks become more active.
This smooth transition allows individuals to move between internal thoughts and external demands efficiently.
The Default Mode Network in Classical ADHD
According to Dr. Amen's SPECT observations and findings from broader neuroscience research, individuals with Classical ADHD often have difficulty suppressing internally directed brain activity when trying to concentrate.
During tasks that require focus:
- Attention-control networks may become underactive.
- Internal thoughts may continue competing for attention.
- The brain may switch frequently between external tasks and internal distractions.
As a result, individuals may experience:
- Frequent daydreaming
- Wandering thoughts
- Difficulty staying present
- Losing track of conversations
- Trouble sustaining attention
Rather than maintaining stable focus, the brain repeatedly shifts between the task and internally generated thoughts.
This may help explain why people with Classical ADHD often report knowing what they should be doing but finding their minds drifting elsewhere.
The Default Mode Network in Overfocused ADD
Overfocused ADD presents a different pattern.
According to Dr. Amen's framework, individuals with Overfocused ADD often demonstrate increased persistence within attention and cognitive-control networks.
When combined with strong internally directed thinking, the result may be excessive mental fixation.
Instead of attention drifting randomly, attention becomes locked onto specific thoughts, worries, concerns, or routines.
As a result, individuals may experience:
- Repetitive thinking
- Rumination
- Excessive self-analysis
- Persistent worry
- Difficulty shifting mental focus
- Obsessive thought patterns
In this subtype, the challenge is often not mind wandering but becoming trapped within a narrow range of internal thoughts.
Mind Wandering vs. Mental Sticking
One useful way to understand the difference is through the concepts of wandering and sticking.
In Classical ADHD:
- Thoughts move constantly.
- Attention shifts rapidly.
- Internal distractions frequently interrupt tasks.
In Overfocused ADD:
- Thoughts persist.
- Attention remains locked.
- Internal concerns become difficult to release.
Both individuals may appear distracted from the outside, but the underlying brain processes are very different.
One mind wanders.
The other becomes stuck.
The Relationship Between the DMN and Hyperfocus
The Default Mode Network may also play a role in hyperfocus.
In Classical ADHD, highly engaging activities may temporarily suppress competing internal distractions, allowing attention networks to dominate.
The result can be intense concentration on stimulating activities.
In Overfocused ADD, hyperfocus may emerge from excessive persistence of internally driven attention.
The individual may become deeply absorbed in:
- Personal interests
- Specific goals
- Worries
- Emotional conflicts
- Repetitive thoughts
In both cases, attention becomes highly concentrated, but the mechanisms may differ.
Emotional Effects of Default Mode Network Activity
Because the DMN is involved in self-reflection, excessive internal focus can influence emotional well-being.
Individuals with Classical ADHD may experience:
- Distracting thoughts
- Difficulty staying engaged
- Mental restlessness
Individuals with Overfocused ADD may experience:
- Self-criticism
- Rumination
- Persistent worry
- Emotional overanalysis
These differences can significantly affect daily functioning and relationships.
What SPECT Scans Suggest
According to Dr. Amen's observations:
Classical ADHD
- Underactive attention-control systems
- Frequent mental drifting
- Difficulty suppressing internal distractions
- Mind wandering during tasks
Overfocused ADD
- Increased persistence of thought patterns
- Difficulty shifting attention
- Repetitive internal focus
- Mental rigidity
Although SPECT imaging does not directly measure the Default Mode Network in the same way functional MRI studies do, the patterns observed by Dr. Amen may help explain differences in internally directed attention across ADHD subtypes.
What Mainstream Neuroscience Says
Modern neuroscience has identified altered interactions between attention networks and the Default Mode Network in many individuals with ADHD.
Researchers often describe ADHD as involving difficulties switching efficiently between task-focused networks and internally focused networks.
However, the specific ADHD subtypes proposed by Dr. Amen, including Overfocused ADD, are not recognized diagnoses in the current edition of the Diagnostic and Statistical Manual of Mental Disorders.
His framework represents a brain-based model derived from clinical observations and SPECT imaging rather than official psychiatric classifications.
Understanding the Internal Experience of ADHD
Dr. Amen's work highlights an important reality: attention difficulties are not always about an inability to focus.
In Classical ADHD, attention may be pulled away by a constantly wandering mind.
In Overfocused ADD, attention may become trapped by persistent internal thoughts and concerns.
One brain struggles because thoughts move too freely.
The other struggles because thoughts do not move enough.
By exploring the role of the Default Mode Network, Dr. Amen's observations provide a useful perspective on why attention can be disrupted in very different ways and why ADHD experiences vary so dramatically from one person to another.