The BIS/BAS/Fight Flight Freeze System

• 1. The Gray BIS/BAS/FFS System
  • 1.1. Reinforcement Sensitivity Theory (RST)
    • 1.1.1. The modified RST (Gray, 2000)
    • 1.1.2. The original RST (Gray, 1990)
• 2. Behavioural Inhibition System (BIS)
  • 2.1. BIS according to the old RST
    • 2.1.1. Activation of the BIS
    • 2.1.2. Effects of the BIS
  • 2.2. The BIS according to the new RST
  • 2.3. BIS and neurophysiological correlates
• 3. Behavioural Activation System (BAS)
  • 3.1. BAS according to old as well as new RST
  • 3.2. Effects of the BAS
  • 3.3. Neurophysiological correlates of the BAS system
• 4. Fight-Flight-Freeze-System (FFFS) according to new RST

1. The Gray BIS/BAS/FFS System¶

Mammalian responses to stress are not uniform.
According to the fight/flight stress model (by Connor (1932) and later Gray, who combined it with the BIS/BAS model → RST of 1990, revised 2000), there are 2 to 3 main groups of stress responses:

The BAS type reacts to stress with attack.
The FFFS type reacts to stress by fleeing or playing dead.
According to Gray’s (2000) revised Reinforcement Sensitivity Theory (RST), the BIS system no longer responds to stimuli from the outside, but only becomes active when the BIS and FFFS systems have both been activated. The BIS system is responsible for the trade-off between BAS and FFFS.

The original Fight/Flight system was extended by the Freeze component to FFFS.

1.1. Reinforcement Sensitivity Theory (RST)¶

Whether BIS and BAS are independent of each other, i.e., BIS and BAS can both be low or differentially high (so Gray), or whether BIS and BAS are the poles of a unitary entity within which they correlate with each other depending on the state (Corr), i.e., are rigidly connected rather like a playground seesaw, was a matter of dispute. The question, meanwhile, is likely to be obsolete in the case of the newer RST, because in the latter the BIS and FFFS must necessarily be active simultaneously in order to offer the BIS alternative courses of action. More recent voices consistently regard the systems as independent of each other.⁵⁶

1.1.1. The modified RST (Gray, 2000)¶

In 2000, Gray modified the reinforcement sensitivity theory (RST) he postulated, primarily with respect to the task of the BIS.

According to the modified RST, the BAS and FFFS are activated simultaneously and independently by new stimuli. The BAS responds to reward stimuli, the FFFS to all Forms of punishment stimuli. In contrast, the BIS is no longer activated by stimuli themselves, but only by a simultaneous activation of BAS and FFFS. The BIS is then activated by conflicts of BAS and FFFS and is used to weigh which system should be given preference for action. At the same time, the BIS activates attention to the environment to provide cues for decision making.⁷⁸

According to this, impulsivity can be described as high extraversion with high emotional lability (neuroticism), resulting in high sensitivity to reward (highly responsive BAS).

1.1.2. The original RST (Gray, 1990)¶

The “old” RST, according to which the BAS system should respond to reward stimuli, the BIS to punishment stimuli and non-reward, and the FFS to existentially threatening stimuli, with these three systems acting independently, could not conclusively explain quite a few responses.

2. Behavioural Inhibition System (BIS)¶

2.1. BIS according to the old RST¶

The Behavioural Inhibition System correlates with the personality traits⁹

• Anxiety
  • As a weakened form of neuroticism
  • Trait Sensitivity of Punishment (SP) Marker
• Introversion (as the antithesis of BAS Extraversion)
• Fear

The BIS maps receptivity to punishment, non-reward, and unknown stimuli (conditioned aversive stimuli).

2.1.1. Activation of the BIS¶

The BIS is activated by

• Conditioned stimuli for
  • Punishment
  • Frustrating non-reward
  • New, unexpected stimuli

These trigger behavioral inhibition via the BIS.

The BIS is noradrenergic-cholinergic-serotonergic controlled¹⁰ and may be impaired by anxiolytics.¹¹

2.1.2. Effects of the BIS¶

People with high BIS report more negative experiences in a diary study and experience them more negatively than comparison groups.¹²
People with high BIS evaluate negative social experiences more negatively. They invest more to avoid them and experience negative experiences more intensely.¹³, page 227, with further evidence))

People with high BIS set negative goals more often. Example in the social domain: “I don’t want to be alone” instead of “I want to have a partner.”¹³, page 227, with further evidence))

Nevertheless, the choice of (here: social) goals is a better predictor of (here: social) success than the measure of sensitivity to punishment or reward (BIS and BAS).¹³, page 227, with further evidence))

2.2. The BIS according to the new RST¶

See above under 1.1.1.

2.3. BIS and neurophysiological correlates¶

Higher BIS correlates with greater right prefrontal activation, shows lower natural killer (NK) cell activity, and responds more strongly to negative emotional stimuli.¹⁴

Neurologically, Gray locates the BIS in the septo-hippocampal system (SHS),¹⁵ consisting of

• Hippocampus (limbic system)¹⁵
• Septal nuclei¹⁵
• Connections to the cingulate cortex, part of the frontomedial PFC¹⁵
• Connections to the PFC¹⁵
• Amygdala¹⁶

An activated BIS increases non-specific arousal, which leads to a focus of attention on currently relevant events.¹⁷
High anxiety and increased punishment sensitivity are particularly characterized by high synchronization of hippocampus and amygdala in the theta EEG frequency band.¹⁸ With a reduction of anxiety by new conditioning, the synchronization of hippocampus and amygdala decreases at the same time.¹⁹²⁰

Depression and anxiety disorders are associated with sensitized BIS.²¹ A sensitized BIS is associated with increased punishment sensitivity and an enlarged hippocampus and amygdala.²²¹⁸

Anxiolytics (anxiety-reducing drugs) decrease the excitability of the amygdala.²³

However, the BIS system can also be impaired by anxiolytics.²⁴

The BIS is controlled by the neurotransmitters

• Norepinephrine¹⁵²⁵¹⁷
• Serotonin¹⁵²⁵¹⁷
• Acetylcholine²⁵

controlled, with norepinephrine and serotonin associated with hypothalamic-pituitary-adrenal (HPA) axis activity leading to cortisol release from the adrenal gland.²⁶ In healthy children, activation of the BIS in response to punishment is associated with increased cortisol levels following difficult situations.²⁷

A summary of the neurological correlates of BIS is shown by Chiossi.²⁸

3. Behavioural Activation System (BAS)¶

3.1. BAS according to old as well as new RST¶

According to Gray’s Reinforcement Sensitivity Theory (RST), Drive, Reward Responsiveness, Fun Seeking²⁹ correlate with the level of activation of the BAS to a given stimulus.
The BAS responds to conditioned stimuli for reward and non-punishment, resulting in approach behavior and general behavioral activation.³⁰³¹

The Behavioural Activation System correlates with the personality trait Impulsivity as a weakened form of Extraversion and maps sensitivity to reward stimuli.³²³³

When the BAS is activated, this leads to a feeling of reward similar to that which occurs after the use of cocaine, amphetamines, heroin or alcohol.³⁴ These rewards are all linked to the dopaminergic system.

3.2. Effects of the BAS¶

People with a high BAS are more likely to report positive experiences than a comparison group in a diary study.¹²
People with high BAS are more likely to set positive goals. Example in the social domain: “I want to meet new people” instead of “I don’t want to be alone.”¹³, page 227, with further evidence))
Nevertheless, as written earlier, the choice of (here: social) goals is a better predictor of (here: social) success than the measure of sensitivity to punishment or reward (BIS and BAS).¹³, page 227, with further evidence))

3.3. Neurophysiological correlates of the BAS system¶

BAS is dopaminergically controlled primarily by the meso-cortical pathway.²⁵

The BAS is neurologically controlled by processes that occur in the brain areas of

• Basal Ganglia
  • Pallidum
    • Dorsal
    • Ventral
  • Striatum
    • Dorsal
    • Ventral
• Dopaminergic neural pathways

lie³⁵

That BAS is dopaminergically controlled primarily through the meso-cortical pathway²⁵ explains the vulnerability of the reward system in ADHD due to the dopaminergic dysfunction known to occur in ADHD.

A jump-start of the BAS is reflected in an increase in heart rate³⁶³⁷ and skin conductance elevation, as well as changes in the startle reflex.³⁸

Children with the ADHD-HI subtype and with social disorders were found to have decreased activity of BIS and increased activity of BAS.³⁹²⁶ Under the new RST, it is likely that FFFS, rather than BIS, is decreased.
The response to recurrent reward stimuli was enhanced, even if these had been replaced by aversive stimuli in the meantime. ⁴⁰

4. Fight-Flight-Freeze-System (FFFS) according to new RST¶

The FFFS correlates with panic and fear (threat), unconditioned aversive stimuli. Primary negative reinforcers are accompanied by negative emotions such as horror, panic, and anger and trigger flight (Flight), freeze (Freeze), or fight (Fight).⁴¹
The FFFS is anchored in the vegetative nervous system.

The therapy method of Mindfulness-Based Stress Reduction (MBSR), which is recognized for ADHD, is vegetatively effective.

The fight-flight-freeze mechanism (which Gray first described) is controlled in the periaqueductal gray of the brain (central cavernous gray). The control mechanism is unknown so far.⁴²