Deepinder Goyal’s temple device: Neurologist debunks it, says not proven, can’t measure blood flow across both sides of the brain

During a recent podcast, Zomato CEO Deepinder Goyal drew attention for wearing a small metallic device worn on his temple, which he described as an experimental health-tech wearable called Temple, claiming to monitor cerebral blood flow in real time and understand brain health.

This experiment follows Goyal’s earlier push for his new research foundation, which advocates the Gravity Ageing Hypothesis. It basically says that gravity ages the brain. It claims that gravity’s lifelong pull on blood circulation in the brain makes it work harder and, therefore, wears it out faster. The device ostensibly tracks the impact of gravity on blood flow in the brain.

The device quickly became a subject of curiosity on social media, with users speculating about its purpose and appearance. The discussion, however, took a sharper turn when a former AIIMS radiologist questioned the device’s efficacy, dismissing it as a “fancy toy for billionaires” with “no scientific standing” and cautioning against investing in unvalidated health technologies. The episode has since sparked a wider debate on the gap between ambitious consumer health wearables and the need for rigorous scientific validation and clinical evidence before such devices are presented as credible medical tools.

According to Dr Praveen Gupta, neurologist, Chairman of Marengo Asia International Institute of Neuro and Spine (MAIINS) Gurugram, a device attached at one point cannot reliably measure blood flow across both sides of the brain or across all arteries, especially the deeper and smaller ones.

The device is being promoted as a brain blood-flow monitoring wearable. There is a lot of discussion because some doctors and public figures are talking about it, but the main concern is that it is not a properly validated device. That means there is no clear scientific proof showing what exactly it measures or how accurate those measurements are. A validated device must be tested under many conditions and shown to measure the intended parameter accurately and consistently. In this case, there is no solid evidence proving that the device reliably measures blood flow inside the brain under different physiological conditions.

The device measures signals from outside the brain. We do not know if it accurately reflects what is happening deep inside the brain. Blood flow differs between the left and right sides of the brain, and between large, small, and tiny arteries. Measuring from one external point cannot reliably represent all these variations.

No. The brain has many arteries with different blood flow patterns. A device attached at one point cannot reliably measure blood flow across both sides of the brain or across all arteries, especially the deeper and smaller ones.

Can cognitive decline or brain degeneration be understood by measuring blood flow at one point?

No. Brain diseases are extremely complex. They involve around 86 billion neurons, one quadrillion synapses, chemical interactions, nutrition, and blood flow. Measuring blood flow at one location cannot explain cognition decline or neurodegeneration.

Reduced blood flow in one artery is not always dangerous. Some people have 100% blockage in one artery and still function normally because other arteries compensate. This shows that blood flow patterns are complex and cannot be judged from a single measurement. Severe blood flow changes may contribute to disease over many years, not over days or weeks. Studying such effects requires long-term research, not short-term observations.

In what medical situations do doctors actually need to measure brain blood flow? Doctors assess brain blood flow in conditions such as stroke, sudden weakness on one side of the body, transient loss of consciousness, recurrent falls, dizziness on standing.

There are several proven tools, including, angiography, CT angiography, MRI angiography, Doppler ultrasound, Transcranial Doppler. These methods are already validated and widely used.

In simple terms, the wearable brain monitor device currently has no proven clinical utility. It lacks a clear scientific hypothesis, robust foundation, and validated data. Proper research involves forming a clear scientific hypothesis, testing it using basic scientific principles, validating it experimentally, testing it on people, conducting long-term (longitudinal) studies to see if results correlate with disease. Brain diseases develop over years, not days or weeks. Long-term studies are required to determine whether any measured data truly predicts or explains disease. The key question is whether the device measures any meaningful data at all — and if it does, whether that data can be reliably used to draw medically useful conclusions.