All this stuff intrigued me coming from the medical field and having dealt with many drugs in my past so I had a desire to be a Berean and check stuff out.
I did some looking on-line about Dr. Caroline Leaf and here are her credentials :
DR. CAROLINE LEAF’S DEGREES
University of Cape Town South Africa
Degree of Bachelor of Science (Logopaedics) - December 1985
University of Pretoria South Africa Masters in Communication Pathology with distinction/cum laude - June 1990
University of Pretoria South Africa Doctor Philosophiae with specialization in Communication Pathology With distinction/cum laude and academic honors - May 1997
I didn't know what a cognitive neuroscientists was so I had to look that up too.
( I can tell you that what Dr. Leaf says about the brain cells being toxic and changing is totally accurate as I sat in on a talk from one of the top psychiatrists in Montreal in 2014 and he showed us pictures of the diseased brain cell that had been affected by negative thinking and how the cell changes when it becomes a healthy thought again )
Here is what Brown's university says about cognitive neuroscience.
Introduction
Cognitive neuroscience is the study of higher cognitive functions in humans and its underlying neural bases. By definition, it is an integrative area of study drawing principally from cognitive science, psychology, neuroscience, and linguistics. There are two broad directions which can be taken in this concentration—one is behavioral/experimental and the other is computational/modeling. In either case, the goal is to understand the nature of cognition from a neural perspective.
Here is the link for Brown's University...It appears to be a legitimate science discipline that is offered by many universities around the world including M.I.T.
Cognitive Neuroscience Concentration | Cognitive, Linguistic & Psychological Sciences (CLPS)
It would appear the person that made the internet article up just doesn't agree with Dr. Leaf's views and thus like most internet blogs - attack the person that had different views then the blogger. It's a common trait unfortunately.